Originally Posted by KL2DC
By releasing the pressure, you keep the turbos spinning a little longer....
With that regard, there is no benefit for a BOV over a DV. BOVs, are not "faster" nor is there any real performance benefit (on this low boost car) except the sweet sound they make. I've done about 5 custom turbo projects and have tried numerous BOV and DV's. My current 1.8L engine puts down 300whp and I'm running a stock DV (diverter valve) while my peak boost is at about 25psi.
The biggest reason people switch to a BOV from a DV is the construction. DV's typically use a rubber diaphram under spring pressure, while a BOV is usually a sealed aluminum piston under spring pressure. I've ripped/melted some DV's by placing them too close to the turbo compressor side. Placing it closer to the throttle body (after the IC) has been better in my experience.
I'm going to be a 335i owner shortly due to the fact I'm a turbo person and its about time BMW got into the turbo/torque game on the gas engines