You see if i'm looking for a car to put a smile on my face which i won't be driving every day i wouldn't be looking at a diesel (sorry to all the diesel fanboys).
The 330i engine is much more eager and sonorous than the 335i engine (earlier or later) but it's smooth and linear, so whilst it sounds good it doesn't feel particularly fast.
The 335i is fast. Plain and simple. Buckets of torque and it pulls hard, and with a remap pulls even harder.
Go drive both and i think you'll very quickly know if you prefer 7k rpm sweet six noise or the overwhelming torque of two turbos...