This seems like a silly debate. There is no doubt the 335i has great ability and potential but it isn't an M3. If you're just looking for quick DD go ahead and buy the 335i. As a performance car it is a dubious argument unless money is no object (and if money were no object you wouldn't be buying a 335i). Modifying the car voids the warranty and kills its resale value (I would never buy a modified vehicle).
Buy an M3.