After experiencing a e46 330ci and then a e46 m3 there is no comparison in the cars, im sure this should be the same way yes the 335 is a little closer but still way off the m3 mark, an M3 is the real deal and I would spend the money on it if I had that much money to throw around.
Just as a comparision the official 335 lap time of the nurburgring is 8.26, the new m3 is 8.05, thats a pretty big difference on that track. Even the e46 m3 came in at 8.22 so its still faster then a 335.