The better driver will win. And for a single driver, the one who prefers a partiular driving style... Those two cars are way closer matched than you are giving credit to. I have seen them go head to head on tracks across the country in One Lap a few years ago... the GTR, Porsche, and the C6Z were neck and neck every track, guy with the least problems that day ended up winning most times.
Weird, I have driven a lot of sports cars, and I would rank the corvette as one of the most comfortable from a commuter standpoint.... GTR is nice too.
Again, purely subjective... I would put $$$ that a modified c6z will turn as many (if maybe different people) heads as a modified GTR....
Or into different things? Both are GREAT cars, and on very equal platforms when it comes to performance, and status (import guys will like GTR more, 'muricans will like C6Z more)