The 3.8 is definitely faster, but the engine is right on the ragged edge and seems to me it fails more regularly than the 3.6. Torque is 295 ft-ln vs. 265, both at 4700 rpm but the 3.8 is much stronger, 12 to 15%, in the 3000 to 5000 rpm range. It will cost $10,000 more to import an M5 from Europe.