Beau,
The short answer is that most brands are largely the same, and will perform well. As long as it is a bi-leaflet mechanical valve, made with pyrolytic carbon, it's good. Some of the major brands out there are St Jude, ATS, On-X and Carbo Medics. Most surgeons have some preference but the bottom line is there is no data that says one is vastly better than another. I have an On-X, and it claims to be better in a number of areas, but this has yet to be proven. St. Judes have been around for a long time and they have been proven to work for up to 30 years, I think. Some people think ATS valves are the quietest. Carbo Medics valves look really cool!
Do some research and decide what's best for you, then see what your surgeon is comfortable putting in. I think the skill of the surgeon is the most important factor in success. I chose On-X because I though some of the new features might be proven to be a benefit at some point. They also sent me a cool carbon ring.
Best wishes to you in your search!
-Steve