MKSGR:
Quality always comes at a certain price...
That sums it up. With Porsche, most of the premium cost is quality. With Ferrari its mostly style and exclusivity. With Corvette, its bang for the buck.
I know I'm no expert here - you guys know way more than I do (including Nick ), but I think with Porsche (particularly in the GT cars) you get a more solid ready-to-track construction, that other street car builds short cut. That's been my impression particularly with corvettes (at least in the past).
For example, I know a fairly capable DE instructor who's been driving a vette for years out of love for the all-american icon that it is. He's been reparing, replacing, upgrading all kinds of components on his dearest love for years. His first and smartest investment was a trailer so he could get it home reliably...
(He has finally switch over to a 2005 997.1 C2S though, but that's not really my point.)
To paraphrase Ben Collins during his comparison of the GT2RS, MP4-12C, 458, SLS, R8v10, and Gallardo: "the Porsche is the only one I would treat this way lap after lap."