Here:

http://www.935motorsports.com/bovmediaX.htm

and

http://www.alltrac.net/tuning/blowoffvalve.html

You shouldn't really pick a blow off valve just because of its sounds and/or looks. However, the HKS and Tial are excellent BOVs. Greddy is nice too, but the diaphragms have been known to have issues and they leak at a lower psi than the Tial or HKS. Blitz DD is also nice, but I don't know if it can be recirculated. Same goes for the Apexi Dual Chamber.

I personally liked the HKS, because of it's "reverse pull" design, versus the "push design" that all the other bov's use. That means that you won't have to worry about the HKS leaking any boost. They have been rated to hold alot of power as well and have great reliability.

Enjoy. I've always been a fan of the Tial and HKS SSQBOV (What I have on my car).