It depends. Just how important is razor sharp handling to you? Do you really need that third pedal?
Although I love the GTS, get the C63. From what every single review has said the handling is vastly improved, it looks fantastic, and (like all C63s) a few bolt-ons will make it more of a monster than it already is - sounds like heaven on 4 wheels to me. But if you answered something to the extent of "they're top priority" to the above questions, you should give that Cayman R a test drive. The 991 is already here so there really isn't a reason to get a new 997.2 unless you love it that much. Good luck!
Stop putting stuff like painted reflectors and premium package in your signature. You're embarrassing.