I'm a bit on the fence on this one... BMW say that the Performance Exhaust is more "free-flowing" than the standard one and claim about 5hp/3tq in their description so I think it probably is baffled differently/less.
BMW Performance Exhaust
Mine definitely has more noise and my butt dyno says its breathing a little better. That could be my imagination though.
Having said that, we all know that the Cats in the DPs are the biggest restrictor so my guess would be that that would be a more important factor...