Depends upon what you're going for. If you're in it for performance and cornering perfection- get an N54 coupe like others said.
The only N54 still in production is the 335iS, and I THINK 2009 was the last year for the N54 in any other E9x.
http://www.vanguard-performance.com/research/bmw-n54-vs-n55/
For me, the added weight was worth it for those beautiful seasonable days cruising with my top down, not to mention the hardtop going up and down is an engineering marvel that is a riot to watch, and never gets old
