I've owned a tuned 335i and a C63. Both have gobs of torque but neither possesses the unique feel of the M3s v8. It just feels different and more special than other road cars.
Handling wise, the M3 spanks the C63 and has a much more solid feel (as do most BMWs compared to other brands).
Disclaimer: Anything said by me and/or about my car on this website or any related websites, about modifications or motorsports, is only to gain acceptance from my peers, and does not actually represent anything actually existing on my car, and thus, cannot be held against me in any issues.