OK, I'm lucky enough to have a e92 335i (with SS Turbo Tuner) and a e92 M3 right outside my door.
I have driven both to death and the difference is quite simple:
- The M3 has less torque down low, makes more power up top, and is, a race car that you can drive on the street. It feels tighter and simply a bit more brutal (brakes, suspension, etc). It sounds sweet and looks aggressive.
BMW 335i +SSTT:
- MUCH more low down torque and delivers its power in a more "street car" like fashion. The 335 is a VERY fast street car - not a race car - the M3's V8 is faster if you can get it over 5000rpm. Under 5000rpm, you will be eating the 335's dust. The 335 is softer and more street friendly than the M3 - but still blows the doors off most other street cars out there.
So, that is my take on the 335 vs M3 discussion - from someone who has both on hand to drive back to back. Both are GREAT cars.
2008 BMW e90 M3 6MT
1990 BMW e30 325i 5MT