I had the same battle and the conclusion was.
If your doing M6 do the Coupe
If you want 4 door do the M5. The GC is sexi! But long..
P.s I picked the Coupe
F13 M6 Sakhir Orange
I get compliments ALL the time!!
P.s I'm 6"3 210lbs and on rough days it kinda sucks going in and out but oh is it worth it. Once Inside plenty of room!
Can't go wrong with any really. Good luck!