The race version sounds great, definately call Nate@IND and he can give you the best details since IND since they are a master distributor of all Eisenmann exhausts. He can give better insight on comparison to the M5 Eisenmann exhaust.
I don't think you would be dissappointed at all if you went with another Eisenmann again.
16' M4 GTS Frozen Dark Grey
14' i8 Sophisto Grey Pure Impulse World
08' E92 M3 Jerez Black