As Mike said, all TD's get their stock from the same manufacturers. That being said, there are several types of TD's. Large, dealers with huge selections - e.g. Trusty Time and PureTime. Their web sites offer huge numbers of models. Smaller TD's - e.g. Intime and Torobravo. These offer a more limited selection of high quality pieces and some suggest this allows them to provide more personalized service. Then there are those TD's that will fulfill orders by email requests only, with no formal web site. e.g. Sead.
Which you choose is purely a matter of personal preference. I have purchased many pieces from Trusty, Toro and Intime. All have been a pleasure to deal with. If I had to choose one, it would be Intime, just because Ryan is super quick to respond and seems to be very selective when choosing a piece for me. He has often mention rejecting several samples BEFORE sending me QC pics.
Also remember, even though the smaller TD's may not offer something on their Web Site, they will be more than happy to find something for you if you send the a detailed link of what you're after. The one thing I would suggest is that you find your preferred TD and stick with them to develop a relationship. That will go a long way should the day come where you experience problems.