If I were in the market for a C63 I would definitely go for a 2012+. I actually prefer the pre-2012's exterior, but the MCT makes the car much, much better IMHO. The old trans in manual mode was a bit disappointing for a car of that caliber.
The Vette feels big and the steering is quite light and vague, but once you get used to the car it is pretty easy to place it. They corner flat, have great grip, and are animals on the track. Hard to beat so much power in a 31xx lbs (z06) car. And the trunk is surprisingly practical - I've fit all sorts of things in there that I didn't think was possible, e.g. 2 sets of dual catback exhausts. Also don't forget that the Vette can be much better with gas than your other choices (though I'm not very sure about the Boss)
If you are looking for a relatively comfy DD with more than 2 seats the C63 would be my second choice. Nothing like the 6.2's torque and SOUND! Not to mention with a tune you pick up 40-50whp IIRC and traps damn near 120mph.