I've driven both before deciding to get a 3 (e92).
+ Feels quicker on its feet with similar wheel size and tires
-Don't really notice the difference in straight line acceleration TBH
-Twitchy handling at the limit compared to the 3
-Small storage space
-Styling (subjective of course)
+More stable at high speeds
+Less twitchy and more predictable at the limit
+more room inside
Overall the E92 is a car I can enjoy more on a daily basis than the E87. It is more predictable at the limit, which makes me more comfortable playing at the limit, which makes the car more fun for me. It was no contest in my eyes, but after all, it's your car.
Go drive them both, then decide!