I have had 20's, 19's, and 18's. From a style perspective... You will notice that many people on this forum have been trending towards smaller wheels for the track oriented look. 20's are more of a street style look. 19's and 18's are your best option from a true performance perspective. You probably already know the negatives of 20's - worse ride quality, higher cost wheels and tires, more susceptible to damage, higher weight, lower grip, and you are much more limited in tire sizing (255's are widest option for the front on 20's while you can run 275's with 18's or 19's). My opinion is that 20's can look good and, if you buy a light-weight wheel, the negative performance impact can be minimal. That being said, I would not get 20's again. I honestly think 19's look better and 18's look especially good on lowered cars. If they don't look better then there is no point IMO. I hope this helps.
'13 M3 - Silverstone II - Sold
'04 M3 - Jet Black - BBS E88, KW Clubsports
Last edited by slicer; 11-21-2012 at 01:03 PM.