Hi - While there are many pros to using aset images, your question relates more to the cons - - so for the sake of brevity, I'll only mention some reasons why the images may be different...so keep in mind that this isn't a balanced/complete explanation on both the pros/cons of reflector scopes.
Reflector scope images can be quite difficult to interpret sometimes as there can be quite a bit of variation depending on many subjective variables (background/lighting/distance/camera quality/skill/position of stone/etc). Unless you are comparing 2 images that have been produced in the same environment, with the same equipment, they can sometimes be misleading - so in the case where aset images have been taken in different conditions, for the average consumer, it is difficult to form a conclusive opinion.
You can have two very well cut diamonds that look very different depending on the aset images...I've seen quite a few stones get knocked back for nothing more than poor aset photography...
So concentrate on the contrast/symmetry/pattern/colours/etc:
Blue is directly overhead, green is from low angles and red is in the middle.
-Blue – Dark contrast areas that indicate obscured light (from the head of the viewer, the camera lenses, etc.)
-Red – The most direct and intense light return. This indicates light reflecting from the 45-75 degree range.
-Green – Reflected light, not as intense as direct light, representing the light return from the horizon to 45 degrees. Green is not failure, even though people tend to think so.
-Black/white - Leakage
Keep in mind that they’re not fool proof even as ‘excellent’ because images don't always translate into real life views - and it also largely depends on your interpretation of what is ‘beautiful’ - do you prefer more dispersion, more sparkle, or more brightness?
For these images specifically, I would suggest that the main difference for the 'lighter' ones is because they have been backlit on a white background rather than a dark background.
...just re-read my post..so much for brevity

...I need to take a page out of Gypsys book on how to be concise...
Hope this helps