Having owned my F30 (335i) for a few weeks I am pleasantly surprised of how well it drives comfort wise. I would even say that it is better than the E60. But the 6er is a notch above that.
You can't go wrong with any of the two cars. But for me a 6er is a better car, but if you don't want to spend that extra money the F30 i still an awesome automobile for the money.