Just because the Porsche, for me anyways, seems like it will age a little better than the Z06. I'm not talking 5-10 years, more like 20-30.
That and I look at the 80's and 90's Porsche's and I'm like wow I'd love to try one of those out, unlike most 80's and 90's Corvettes (then again, the newer Corvettes are leaps and bounds ahead of the past one). Honestly, typing this out is making me re-think my answer, lol.