Also came from an '07 335i (tune, plus many other mods) and the M3 really does stand apart. From the better chassis and LSD to the more refined/higher quality interior (L.O.V.E the seats and the steering wheel is much better).
The biggest difference, however, is the engine. If your 335 is stock, it will be better in EVERY way. If it's modded, I still give the M3 the edge due to it's superior linear power, eagerness to rev/respond and sound.
Congrats and merry Christmas to you!
M in love