I may have replied to your 1Addicts post
I sold my 135 and now own a 335. I'm ok with it but I miss my 135 !!! The wife hated the 135i b/c I had Cobb Stage II with FBO's...near 400 rwhp. The Cobb made it unbearable for my wife and she claimed she experienced whiplash each time she drove
I have GIAC Stage II on my 335, not as fast, but a ton smoother. My wife doesnt even notice the increase in power b/c of its overall smoothness. I should have installed GIAC Stage II on my 135
135i - lighter, quicker, overall a better track car, but the suspension needs upgrading. EG I upgraded suspension with coilovers, M3 rear subframe bushings (necessary to remove the annoying bounce), M3 front control arm kit, front and rear sway bars, rear toe arms, and non-RFTs.
335i sedan - roomier, 4 doors (still roomier if you have a coupe), smoother ride (I have Sport suspension) even with RFTs. I am upgrading my suspension to either BMW Performance or Koni's + BMW Perf springs.
Overall I would say the 135i is a lot more fun to drive and will put a smile on your face each time you drive. The 335 is roomier and a more comfortable ride. I would recommend the 135 if you track and use as a daily or just want to have fun while you drive, the 328 or 335 (sedan or coupe) if you just want a good DD.
FYI...if you track (135i) an LSD would be recommended before you even add a tune