I’ve driven both many times because they kept giving me an M235 as a loaner for my 1M when it first came out and I owned a 135 in the past—-NO question the 135.
To me the M235 always felt very detached and boring to drive. Horrible steering and really no sense of feel for the car.
It may be faster than a 135 but it isn’t worth it to lose basically everything that makes a small BMW fun. I also think the 135 is a much better looking car—a more classic 3-box BMW design and smaller.
This is a win-win for you—-get the more fun car cheaper!
