So I didnt bother to read the whole thread, so if this has been said, then whatever.
If money isnt 'really' an issue, then what it really boils down to is what you want to do with the car.
As someone who has driven, been in and/or around on the track (road course), they are both terrific cars, but feel miles apart. The torque, growl, and corner exit of the c6z is hard to beat, but the handling and refinement of the porsche in the turns is hard to ignore. Having followed One Lap the last few years, I can tell you it is always a battle for the overall track between a porsche, a vette, and now the skylines. All three are typically right on top of each other. 2011 was kind of wacky with break down etc.., but in 2010 a couple 911 turbos and a couple c6z's were battling it out almost every track event and the porsche guys took it more often.
So they both perform neck and neck, so it really is more of a feel thing there. I, for one, prefer the brute force of the corvette, just puts a bigger smile on my face.
Now if it isnt for racing, and is for just driving around town, 7 out of 10 yuppies would choose the porsche. The porsche feels and looks more refined, but depending on your size may be less comfortable. One of my problems at 6'4" is that w/ a helmet my head hits the headliner in most porsches. Porsche has the name and look for the exclusive feel to and/or if you feel the need to impress people by telling them what car you drive.
If the car is for a little bit of both, more more for making 'you' happy.... I think the c6z is a very hard car to beat. and the extra $40k can get you a lot of other goodies to make the grin even bigger.
Oh and another thing, not that it matters if you ahve the cash to drop anyway. But the maintenance requirement and cost for the porsche is exponentially greater. And if you like to work on cars yourself, the 996 is a PITA to work on.