Think it would depend on what colour you're looking for?
I love Leibish, but I would use them for either rarer colours (pink, blue, red, green, orange) or for high quality yellows and larger stones.
They seem a touch more expensive on some browns and grays vs other sites. But perhaps they are carrying finer specimens. I'm not sure. It is hard to compare without viewing the stones in person, and I can't vouch for the accuracy of other vendor's photos.
Colors I am interested in are fancy blue, green, pink, orange, purple/violet - small (under 0.15 cts) and round. For colors other than purple or violet, I would prefer no modifying colors and I would like to have the saturation be at least Fancy. I have a project in mind for these. I have been in touch with Leibish and they are keeping their eye out for me but did not know if I should conisder anyone else since these will not be easy to find.
Indeed... if that's what you're after, I think Leibish is a good bet. They are pretty quick to share what they can find.
That violet and orange are going to be costly. Beside them the pink, green and blues are not exactly cheap, but in that size its doable. Not sure if you'll find them in rounds that quick (rounds seem to be most common in the .25-.4 range for FCDs for some odd reason).
Hope you're not in a hurry, and also that you'll share your project with us every step of the way! Langermann has quite the selection of rounds as well, you may want to try them. Though I've not dealt with them before.
I will definitely share the project every step of the way! As I stated before, I have a call into Leibish and I am sure they will be the ones I work with. So excited!
I've had 6 transactions with http://reddiam.com/ They are very easy to work with and are very, very patient. In fact I currently have 2 more FCD's reserved with them.
After looking at the sites, I think that Leibish and Ishay Ben David are the way to go. I have been in communication with both and will let you know what I find!
I have 5 stones from Leibish. I have to agree with everyone else, they are a top-notch vendor. I have purchased from reddiam once before and I too have a stone on the way from them. I would also recommend Denir Diamonds http://www.denirdiamonds.com. I was very pleased with their customer service, fast shipping, and the accuracy of the colors shown in their photos vs. in person.
I've bought stones from Diamonds By Lauren and Leibish. Both are excellent. But I've only had stones *set* into jewelry from DBL so I know their setting work and service is impeccable whereas I know nothing of Leibish's setting process.