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real world examples of poor performing stones

dan1230

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So I know that an ASET or Idealscope can tell you almost everything you need to know about light performance but I'm curious how this translates to the actual appearance and real world performance of the stone under a naked eye. I'm assuming it's fairly difficult to photographically show this but are there any decent video comparisons out there showing the differences between a diamond that would be considered "dull" vs. something with a lot of fire and brilliance?
 

dan1230

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Thanks!
 

Rockdiamond

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HI Dan,
Great question.
TO me the first thing it indicates is exactly how the word "performance" is misleading when used in this context.

Just as an example the WF page linked to.
There's two asscher cuts used in the representation. Which is better?
To me, the one on the right will be a much better "performer"- but if we use the aset, it would seem a slam dunk that the stone on the left "performs" better.
The issue is defining "performance".
I want an Asscher cut with nice steps and prominent corners.
If the quantity of light return is the issue, we should use mirrors, not diamonds.
It's the quality and patterning of light return that gives a stone performance IMO

Another issue- photographs and vidoes are taken using the perspective of the photographer.
In Jon's (GOG) Videos, he is very skilled at broadcasting the look, as he see's it.
But I don't see diamonds that way myself. So I will not shoot them the same way.
From the WF page
"Another interesting thing is seen in the “glamour images”. The purpose of these images is to reveal the beauty of the diamond and the photographer works with the diamond until he gets an angle that is most becoming. While both are very pretty, notice how the photographer had to stage the 2.02 to shoot at a very low angle in order to reveal the personality of the stone. That is consistent with what we see in ASET. "

From my perspective, the photographer completely misses the beauty of the 2.02 by photographing it as he did.

This is by no means a knock on how WF , or Jon is representing their idea of performance.
But the point is, performance in diamonds is HEAVILY subjective- especially in fancy shapes.
 

Rockdiamond

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bad-rad-2.jpg

Here's an image of a stone with light performance I did not prefer- the large dark areas in the center- looking like a bow tie- looked bad to me in pics.
 

pyramid

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These would all get fair or poor for cutting. Very Good is a lot better. Not all James Allen diamonds offered are ideal within the Pricescope guideline but if you look at the videos on the site where people have chosen diamonds you cannot tell the difference between cut difference of ideal (one which I know was chosen for this) and other peoples stones and they were not all chosen with pricescope guidelines I am sure. Also the one I was looking at in real life was set in a james allen three stone ring and the centre stone is no better than the side stones chosen for the stock setting although it took a long time searching for all angles and percentages to line up. I remember reading before that Super Ideal cut only makes a small percentage of difference and cannot be seen with the naked eye. Perhaps this is what GIA found when they promoted Excellent cut with large perimeters. This post is helpful however when looking for dark areas in overly deep stones or light leakage around the edges but stones like those would never get a very good grading any way. If you look at aquaintances rings you cannot really notice a Super ideal from an ideal or an ideal from a very good, you can only see it on your own stone in things like the symmetry of the arrows, but you can notice a colorless diamond, it looks whiter like bright snow (though you may not prefer it - it is as noticeable as super cutting is).
 

Texas Leaguer

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Rockdiamond|1472572813|4071455 said:
HI Dan,
Great question.
TO me the first thing it indicates is exactly how the word "performance" is misleading when used in this context.

Just as an example the WF page linked to.
There's two asscher cuts used in the representation. Which is better?
To me, the one on the right will be a much better "performer"- but if we use the aset, it would seem a slam dunk that the stone on the left "performs" better.
The issue is defining "performance".
I want an Asscher cut with nice steps and prominent corners.
If the quantity of light return is the issue, we should use mirrors, not diamonds.
It's the quality and patterning of light return that gives a stone performance IMO

Another issue- photographs and vidoes are taken using the perspective of the photographer.
In Jon's (GOG) Videos, he is very skilled at broadcasting the look, as he see's it.
But I don't see diamonds that way myself. So I will not shoot them the same way.
From the WF page
"Another interesting thing is seen in the “glamour images”. The purpose of these images is to reveal the beauty of the diamond and the photographer works with the diamond until he gets an angle that is most becoming. While both are very pretty, notice how the photographer had to stage the 2.02 to shoot at a very low angle in order to reveal the personality of the stone. That is consistent with what we see in ASET. "

From my perspective, the photographer completely misses the beauty of the 2.02 by photographing it as he did.

This is by no means a knock on how WF , or Jon is representing their idea of performance.
But the point is, performance in diamonds is HEAVILY subjective- especially in fancy shapes.
Performance is not subjective. Beauty is.

Light performance is broken out by component aspects and measured. Brightness, contrast, dispersion, leakage can all be mathematically calculated by ray tracing because light obeys the laws of physics.

Patterns, shapes, color, clarity and other factors all enter into overall beauty, and that judgment is subjective and involves multiple value judgments on the part of the individual.

But light performance can be quantified to a large degree. And while it is only one aspect of diamond beauty, it is generally agreed to be the most important.
 

Rockdiamond

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Texas Leaguer|1472590996|4071562 said:
Rockdiamond|1472572813|4071455 said:
HI Dan,
Great question.
TO me the first thing it indicates is exactly how the word "performance" is misleading when used in this context.

Just as an example the WF page linked to.
There's two asscher cuts used in the representation. Which is better?
To me, the one on the right will be a much better "performer"- but if we use the aset, it would seem a slam dunk that the stone on the left "performs" better.
The issue is defining "performance".
I want an Asscher cut with nice steps and prominent corners.
If the quantity of light return is the issue, we should use mirrors, not diamonds.
It's the quality and patterning of light return that gives a stone performance IMO

Another issue- photographs and vidoes are taken using the perspective of the photographer.
In Jon's (GOG) Videos, he is very skilled at broadcasting the look, as he see's it.
But I don't see diamonds that way myself. So I will not shoot them the same way.
From the WF page
"Another interesting thing is seen in the “glamour images”. The purpose of these images is to reveal the beauty of the diamond and the photographer works with the diamond until he gets an angle that is most becoming. While both are very pretty, notice how the photographer had to stage the 2.02 to shoot at a very low angle in order to reveal the personality of the stone. That is consistent with what we see in ASET. "

From my perspective, the photographer completely misses the beauty of the 2.02 by photographing it as he did.

This is by no means a knock on how WF , or Jon is representing their idea of performance.
But the point is, performance in diamonds is HEAVILY subjective- especially in fancy shapes.
Performance is not subjective. Beauty is.

Light performance is broken out by component aspects and measured. Brightness, contrast, dispersion, leakage can all be mathematically calculated by ray tracing because light obeys the laws of physics.

Patterns, shapes, color, clarity and other factors all enter into overall beauty, and that judgment is subjective and involves multiple value judgments on the part of the individual.

But light performance can be quantified to a large degree. And while it is only one aspect of diamond beauty, it is generally agreed to be the most important.
SO what is the objective measurement of performance Bryan? AGS idea? More red in an ASET? How in the world can you separate a diamond's optical performance into some sort of statistical category? Who agreed that what you're terming "light performance" is "most important"? I find that most people want a diamond for reasons of beauty.
 

dan1230

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Wow certainly a lot of different opinions when it comes to this and I think that's kind of what I was getting at with my original question. I understand (to a degree) the various technical aspects that go into how well a diamond reflects and transmits light because it is well documented but at the end of the day, let's just say i get 2 diamonds side by side-they are both identical in cut quality, polishing, etc... with a identical clarity but 1 scores below a 2 in HCA and the other is much higher due to a steep or shallow table/pavilion-what will that translate to in viewing the diamond with the naked eye.

Perhaps I should just add that the reason I'm bringing this up is because last week I was at a jeweler in the city that a friend of mine recommended and was very nice and helpful. I had emailed him before I came in with what I was looking for including depth, table, and pavilion ranges. He more or less told me that he'll help me find whatever I want in terms of specs but as long I'm looking at something like a GIA triple EX diamond, I shouldn't really be too concerned with all the minor details like angles and percentages. I don't know if i necessarily agree with him-my gut tells me that's a bit of an extreme view but I also don't possess the knowledge to disagree with him either.
 

Texas Leaguer

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Rockdiamond|1472594174|4071587 said:
Texas Leaguer|1472590996|4071562 said:
Rockdiamond|1472572813|4071455 said:
HI Dan,
Great question.
TO me the first thing it indicates is exactly how the word "performance" is misleading when used in this context.

Just as an example the WF page linked to.
There's two asscher cuts used in the representation. Which is better?
To me, the one on the right will be a much better "performer"- but if we use the aset, it would seem a slam dunk that the stone on the left "performs" better.
The issue is defining "performance".
I want an Asscher cut with nice steps and prominent corners.
If the quantity of light return is the issue, we should use mirrors, not diamonds.
It's the quality and patterning of light return that gives a stone performance IMO

Another issue- photographs and vidoes are taken using the perspective of the photographer.
In Jon's (GOG) Videos, he is very skilled at broadcasting the look, as he see's it.
But I don't see diamonds that way myself. So I will not shoot them the same way.
From the WF page
"Another interesting thing is seen in the “glamour images”. The purpose of these images is to reveal the beauty of the diamond and the photographer works with the diamond until he gets an angle that is most becoming. While both are very pretty, notice how the photographer had to stage the 2.02 to shoot at a very low angle in order to reveal the personality of the stone. That is consistent with what we see in ASET. "

From my perspective, the photographer completely misses the beauty of the 2.02 by photographing it as he did.

This is by no means a knock on how WF , or Jon is representing their idea of performance.
But the point is, performance in diamonds is HEAVILY subjective- especially in fancy shapes.
Performance is not subjective. Beauty is.

Light performance is broken out by component aspects and measured. Brightness, contrast, dispersion, leakage can all be mathematically calculated by ray tracing because light obeys the laws of physics.

Patterns, shapes, color, clarity and other factors all enter into overall beauty, and that judgment is subjective and involves multiple value judgments on the part of the individual.

But light performance can be quantified to a large degree. And while it is only one aspect of diamond beauty, it is generally agreed to be the most important.
SO what is the objective measurement of performance Bryan? AGS idea? More red in an ASET? How in the world can you separate a diamond's optical performance into some sort of statistical category? Who agreed that what you're terming "light performance" is "most important"? I find that most people want a diamond for reasons of beauty.
When you are shopping for a car, you may personally find more value in the blue one with the 6 cylinder engine. Someone else finds more value in the green one with the 8 cylinder and sunroof. Neither is wrong. The spec sheet of each vehicle helps in the decision making process.
 

Texas Leaguer

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dan1230|1472594893|4071589 said:
Wow certainly a lot of different opinions when it comes to this and I think that's kind of what I was getting at with my original question. I understand (to a degree) the various technical aspects that go into how well a diamond reflects and transmits light because it is well documented but at the end of the day, let's just say i get 2 diamonds side by side-they are both identical in cut quality, polishing, etc... with a identical clarity but 1 scores below a 2 in HCA and the other is much higher due to a steep or shallow table/pavilion-what will that translate to in viewing the diamond with the naked eye.

Perhaps I should just add that the reason I'm bringing this up is because last week I was at a jeweler in the city that a friend of mine recommended and was very nice and helpful. I had emailed him before I came in with what I was looking for including depth, table, and pavilion ranges. He more or less told me that he'll help me find whatever I want in terms of specs but as long I'm looking at something like a GIA triple EX diamond, I shouldn't really be too concerned with all the minor details like angles and percentages. I don't know if i necessarily agree with him-my gut tells me that's a bit of an extreme view but I also don't possess the knowledge to disagree with him either.
Dan, your question really gets to the heart of the matter and it is the question that countless people coming here and learning about diamonds while in the process of shopping for one, have to answer for themselves.

GIA Triple Ex is a fairly broad range of well cut diamonds. So, depending on your tolerance for cut quality, knowing that it has that grade may be sufficient. But if you believe, as many people here do, that top cut quality is something to strive for because of its impact on diamond beauty, then you have to dig a little deeper on the details and diagnostics.
 

Rockdiamond

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dan1230|1472594893|4071589 said:
Wow certainly a lot of different opinions when it comes to this and I think that's kind of what I was getting at with my original question. I understand (to a degree) the various technical aspects that go into how well a diamond reflects and transmits light because it is well documented but at the end of the day, let's just say i get 2 diamonds side by side-they are both identical in cut quality, polishing, etc... with a identical clarity but 1 scores below a 2 in HCA and the other is much higher due to a steep or shallow table/pavilion-what will that translate to in viewing the diamond with the naked eye.

Perhaps I should just add that the reason I'm bringing this up is because last week I was at a jeweler in the city that a friend of mine recommended and was very nice and helpful. I had emailed him before I came in with what I was looking for including depth, table, and pavilion ranges. He more or less told me that he'll help me find whatever I want in terms of specs but as long I'm looking at something like a GIA triple EX diamond, I shouldn't really be too concerned with all the minor details like angles and percentages. I don't know if i necessarily agree with him-my gut tells me that's a bit of an extreme view but I also don't possess the knowledge to disagree with him either.
Hi Dan,
I am a battle scarred veteran of literally thousands of discussion on this very subject.
I love your question- and clearly I'll get some push back to my perspective.
Your friend is giving you pretty safe advice- particularly if you have the opportunity to view multiple GIA EX cut grade stones in person.
It's likely you'll have a preference for one or another.
And part of what you may be seeing is related to pavilion, crown angles- as well as table size and depth.
Will every consumer pick the same stone? No.
Will a majority of consumers pick a stone with a lower HCA? Maybe- but even if it's true, I suspect the percentages might be 55-45. No way it's 90-10.

Texas Leaguer said:
When you are shopping for a car, you may personally find more value in the blue one with the 6 cylinder engine. Someone else finds more value in the green one with the 8 cylinder and sunroof. Neither is wrong. The spec sheet of each vehicle helps in the decision making process.

Great analogy Bryan, which totally makes my point.
A BWM M4 goes 0-60 in about 4 seconds. The 428i takes about 5.5 seconds. This can be repeatably measured- even tests at different altitudes, or with more passengers, different ambient temperatures, all of which will affect the performance.
If a person drives, or rides in either during an acceleration run, they will certainly feel the difference.

Let's compare this to a diamond's performance as an objective measurement.
Once you let us know the measurements used to determine the performance, we'll need to find out how the diamond performs in real world lighting.
Even once you do that, we can surely agree that not all buyers will identify the stone you claim has the best performance, over another stone shown to have lesser performance, based on the barometer you're using.

The point is- the performance of the car is demonstrated using objective measurements.
When considering a diamond, any aspects other than the dimensions and measurement will involve subjective judgement.
 

Texas Leaguer

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Rockdiamond|1472596541|4071606 said:
dan1230|1472594893|4071589 said:

Great analogy Bryan, which totally makes my point.
A BWM M4 goes 0-60 in about 4 seconds. The 428i takes about 5.5 seconds. This can be repeatably measured- even tests at different altitudes, or with more passengers, different ambient temperatures, all of which will affect the performance.
If a person drives, or rides in either during an acceleration run, they will certainly feel the difference.

Let's compare this to a diamond's performance as an objective measurement.
Once you let us know the measurements used to determine the performance, we'll need to find out how the diamond performs in real world lighting.
Even once you do that, we can surely agree that not all buyers will identify the stone you claim has the best performance, over another stone shown to have lesser performance, based on the barometer you're using.

The point is- the performance of the car is demonstrated using objective measurements.
When considering a diamond, any aspects other than the dimensions and measurement will involve subjective judgement.
No, actually you made my point. It's well known that you will get different results when driving a car in different conditions. Different acceleration, gas mileage, etc, depending on numerous variables.

But that does not make the spec sheet any less valuable to the car buyer.
 

Rockdiamond

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OK Bryan- so can you show me the objective measurement for the diamond- and the tolerances please?
Any objective measurement has tolerances, yes?
 

Rockdiamond

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I understand why AGSL has created, and utilized the methodology.
There's a lot to be said for modern cut grading. Yet, there's also a lot about it that can easily be taken out of context by someone who has not looked at actual diamonds and seen the implications.
That's why I feel the determination of light performance using current methods- as good as they are, should be looked at as subjective, as opposed to absolute, and objective.
 

Texas Leaguer

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Rockdiamond|1472598287|4071618 said:
OK Bryan- so can you show me the objective measurement for the diamond- and the tolerances please?
Any objective measurement has tolerances, yes?
An example of objective measurement of the components of light performance in a diamond is running a ray tracer with 40,000 virtual light rays on a 3D scan of an individual diamond at a variety of tilt angles and measuring brightness, contrast, dispersion and leakage.

By tolerances I assume you mean how much deviation is tolerated between one grade and another. In the 0-10 AGS system the tolerance is a deduction totalling more than .5 across those characteristics. So deductions totalling .51 would drop the grade from Ideal to AGS1. Deductions totalling 1.51 would drop the grade to AGS2 and so on.

Attached is a sample light performance grading spreadsheet with three actual diamonds. One that had a deduction for dispersion but did not exceed the tolerance for a grade reduction. One that had two deductions (contrast and dispersion) totalling more than 1 but less than 1.5 so it received only a one grade reduction. (The first column with numbers is the final grade). The last stone had no deductions for any attribute.

Shape FinalGrade Cumulative Brightness Dispersion Contrast Leakage WeightRatio Durability Girdle Culet Tilt Symmetry Polish
Round 0 0.411 0 0.411 0 0 0 0 0 0 0 0 0
Round 1 1.1705 0 0.7715 0.399 0 0 0 0 0 0 0 0
Round 0 0 0 0 0 0 0 0 0 0 0 0 0

Sorry the columns did not line up with the headers in my copy/paste, but if you work at it you can connect them.
 

Texas Leaguer

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Rockdiamond|1472599601|4071628 said:
I understand why AGSL has created, and utilized the methodology.
There's a lot to be said for modern cut grading. Yet, there's also a lot about it that can easily be taken out of context by someone who has not looked at actual diamonds and seen the implications.
That's why I feel the determination of light performance using current methods- as good as they are, should be looked at as subjective, as opposed to absolute, and objective.
AGSL light performance grading is completely objective. It is all done with math and a computer doing millions of calculations. No human grader is involved.

Arguments can be made around specific assumptions within the grading framework, but you cannot say that the system is subjective.

No grading system can ever be 'absolute', nor have I ever heard anyone claim that one was.
 

flyingpig

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Attached is a sample light performance grading spreadsheet with three actual diamonds. One that had a deduction for dispersion but did not exceed the tolerance for a grade reduction. One that had two deductions (contrast and dispersion) totalling more than 1 but less than 1.5 so it received only a one grade reduction. (The first column with numbers is the final grade). The last stone had no deductions for any attribute.

Shape FinalGrade Cumulative Brightness Dispersion Contrast Leakage WeightRatio Durability Girdle Culet Tilt Symmetry Polish
Round 0 0.411 0 0.411 0 0 0 0 0 0 0 0 0
Round 1 1.1705 0 0.7715 0.399 0 0 0 0 0 0 0 0
Round 0 0 0 0 0 0 0 0 0 0 0 0 0

Thanks for this.

I always wanted to know how AGS's cut grading by deduction works. :dance:
 

Rockdiamond

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Texas Leaguer|1472608363|4071694 said:
Rockdiamond|1472599601|4071628 said:
I understand why AGSL has created, and utilized the methodology.
There's a lot to be said for modern cut grading. Yet, there's also a lot about it that can easily be taken out of context by someone who has not looked at actual diamonds and seen the implications.
That's why I feel the determination of light performance using current methods- as good as they are, should be looked at as subjective, as opposed to absolute, and objective.
AGSL light performance grading is completely objective. It is all done with math and a computer doing millions of calculations. No human grader is involved.

Arguments can be made around specific assumptions within the grading framework, but you cannot say that the system is subjective.

No grading system can ever be 'absolute', nor have I ever heard anyone claim that one was.
I think this is the area of disagreement.
What is 0 deduction?
"0" is not a objective measurement in the way that 425 BHP is. Deciding what is and isn't a deduction is subjective.


Light performance as defined by AGSL is scientific and a lot of work has been put into it.
Respecting that does not necessarily mean agreeing with the manner in which the results have been used.
 

dan1230

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Well I suppose if there was a definitive answer to my question, I wouldn't have been asking it in the first place haha. I'd simply go into a store, pick-out a diamond with the spec I wanted and rest assured it was going to look exactly how I had envisioned. Because there is such a subjective element to the appearance of a diamond I guess it really is just figuring out what is personally important to the buyer (and receiver in the case of an engagement ring) and trying to find the best fit.

I can sort of relate this to what I do at work with imaging systems. Myself and a few imaging scientists and engineers i work with create facial imaging systems for aesthetic medical practices that will allow someone to take a picture and show them either how they'll look with various procedures like botox or other fillers or simply highlight skin damage that can then be treated through various means. From a strictly scientific perspective, there are a number of things we can do to create the ideal lighting environment to highlight a variety of skin features. Similarly, we can apply various color processing and white balance adjustments to create an image that is nearly 100% accurate to that person's skin. In practice, however, we've found that those images tend to be perceived as not aesthetically pleasing. This is a completely subjective opinion but it is an important one unless the images are being used for some sort of photo documentation approval. People tend to like a warmer, slightly pinkish hue to their skin and also prefer softer lighting rather than harsh shadows. Sometimes these values can directly contradict things we are trying to highlight in the skin, sometimes they do not. I can see how diamonds have both a subjective and objective aspect to them that might not always coincide either, despite what all the evidence on paper says.

So at least for me, the takeaway is that I just need to find the right balance that fits my needs and own personal specifications and factor that into my decision rather than strictly looking at X or Y.

Thanks for everyone's inputs!
 

Texas Leaguer

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dan1230|1472644599|4071823 said:
Well I suppose if there was a definitive answer to my question, I wouldn't have been asking it in the first place haha. I'd simply go into a store, pick-out a diamond with the spec I wanted and rest assured it was going to look exactly how I had envisioned. Because there is such a subjective element to the appearance of a diamond I guess it really is just figuring out what is personally important to the buyer (and receiver in the case of an engagement ring) and trying to find the best fit.

I can sort of relate this to what I do at work with imaging systems. Myself and a few imaging scientists and engineers i work with create facial imaging systems for aesthetic medical practices that will allow someone to take a picture and show them either how they'll look with various procedures like botox or other fillers or simply highlight skin damage that can then be treated through various means. From a strictly scientific perspective, there are a number of things we can do to create the ideal lighting environment to highlight a variety of skin features. Similarly, we can apply various color processing and white balance adjustments to create an image that is nearly 100% accurate to that person's skin. In practice, however, we've found that those images tend to be perceived as not aesthetically pleasing. This is a completely subjective opinion but it is an important one unless the images are being used for some sort of photo documentation approval. People tend to like a warmer, slightly pinkish hue to their skin and also prefer softer lighting rather than harsh shadows. Sometimes these values can directly contradict things we are trying to highlight in the skin, sometimes they do not. I can see how diamonds have both a subjective and objective aspect to them that might not always coincide either, despite what all the evidence on paper says.

So at least for me, the takeaway is that I just need to find the right balance that fits my needs and own personal specifications and factor that into my decision rather than strictly looking at X or Y.

Thanks for everyone's inputs!
Very well said.

And interesting work! Thanks for sharing that.
 
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