FWIW I also thought some of the materials on the F30 were significantly cheaper than those in the E90. Specifically the buttons and knobs.
I also thought the doors felt less solid.
Does this make the E90 better? I wouldn't necessarily say that.
I will say that I debated whether to buy my E90 or wait for the F30. While the F30 has some things going for it, I don't regret not waiting at all.