Working for BMW I've driven every product we offer. But for the sake of this comparo I'll concentrate on the cars I drove with the intention to purchase. Ended up with an M coupe (obviously) via a 335i.
Along the way ran into these cars, here's some quick disjointed observations. I can go deeper if asked.
650i 6spd: Don't know what I was thinking, VERY plush with a slight tightness to the handling, solid power. Other than that very underwhelming. does NOT hide its size. Interior has NOT aged well either.
Honda S2000: Manic power band and VERY neutral handling. Awesome at 8/10+...not in traffic. Very hardcore for a daily driver but manageable (I'm also touched in the head). Roadster not ideal for my climate.
Nissan 370Z: Good looking, priced well. Had VERY good road feel and turn-in (indicative of a modern chassis). HORRIBLE interior. Good power but a horrible driving experience...lots of NVH and an engine that begs you NOT to thrash it.
Lotus Elise: Life changing. Best 2nd car in the world. Ruined me for other vehicles. Handling perfect (too perfect..."dangerous" for those with no track or driving school experience). Looks like an exotic, exotic car dealer experience (at least in vancouver, weissach is amazing). Interior is non-existent (didn't care). Tons of NVH (didn't care). Only 135 ft/lbs ( didn't care. moves 1950lbs easily). Deal breaker was servicing (I'm in Edmonton not Vancouver), Rates (straight bank rate) and despite my love I still wanted only one vehicle. I WILL own a Lotus product in the future though no question.
BMW 135i: Pre ordered then canceled after BMW launch drive. Lots of power, modern chassis. Ungainly looks in person. MILES AND MILES of understeer (didn't want to have to re-do suspension and tires on a brand new car). Overall very good but a little "meh" when I was looking for "wow". Excellent DD though.
BMW 335i: VERY GOOD, looks better than the 135i. Overall driving experience a bit better...longer wheel base, less understeer. Got bored after 60 days. N54 has no personality.
BMW M coupe: Ended up with the coupe. Seems to combine everything I'm looking for. Looks exotic, relatively comfortable (for me anyway). Manic personality and motor when required. Overall very happy and in love with it!!