Here's the deal with the BOV's...
The SSQV is my valve of choice. However HKS removed the stem adjustment on the back of the valve on the new SSQVs that came out earlier this year. No more adjusting the valve pressure to combat stalling.
The GReddy Type S and RS are both adjustable which is good however, with the MSP dual valve setup, the RS is a very faint blow off under 10 psi. So someone who wants the BOV sound to go with the BOV, the RS is the quietest. The Type S is louder but it is discontinued.
The Tial valves sound great and have adjustable springs to combat "stalling." And they are the most cost efficient too, they include the flange with the BOV.
http://www.**********.com/TSBOV_p/tsbov.htm