I'm considering both. I used to have an '03 M5, I've had an '03 ZO6. The torque in the corvette was awesome. The new ZO6 will even tromp that. I'm now the proud owner of an '05 645i and am considering an M6. I worry what has been reported with the '06 M5 that the torque at low rpm's will wane for a truly throw you to the back of the seat acceleration, having to wait for the revs to get going. BMW's quality in build and materials are unparalleled, but 7.0 liters of brute force with exceptional fuel economy will be hard to beat. I don't need two 500 hp cars. What a frickin' dilemma.