One key reason I wouldn't be able to own the C63 as a sports coupe/sedan is the fact that there is no manual transmission option.
As far as looks, interior and engine go I think the C63 is a very nice car and given it had a manual I wouldn't mind owning one.
One thing is for sure, every car magazine article and television show published/produced since 2008 can't be wrong on the fact that the M3 is the more engaging/better drivers car. If anyone can find me a magazine article or television show where the C63 (or IS-F or RS4 for that matter) has been declared the better car I would love to have see it!
2011 E90 M3 ZCP - Individual Moonstone/Individual Amarone Extended/Individual Piano Black With Inlay:LINK!!!
1994 Euro E36 M3 Sedan - Daytona Violet/Mulberry:LINK!!!