If I could get away with a 2 door, I personally would get the Caymen. It has that "presence" on the street and feels like your in a light and nimble race car. It just feels more racey and the PDK is sweet.
But for all around use, I love this M3. It feels different but in another good way, solid and predictable and the DCT is also awesome. I think the biggest thing the M3 has over the Caymen is the way you can set it up. 11 settings on the DCT, 3 settings for the dampeners, 2 settings for steering, 3 settings for throttle response. You can set it up for track use, hit a button and have a nice comfortable ride home. The duel personality and multitude of settings for track and street is something to love. Want the soft ride but gutsy throttle and shifting? You can have that whereas (at least the caymen I drove) you had an all or nothing sport setting and comfort setting. I love how I can pick and choose which behaviors I want from each individual setting.
08 GT500 convertible red package (Black w/ Red stripes) /Ford Racing Exhaust /Cold Air Induction 560hp
10 Porsche Cayenne GTS Black w/ Black Wheels 408hp
11 M3 Silverstone w/ Silver Novillo Leather /Tech /Premium /19" /DCT /Ipod 414hp