Part of my reason to switch is my local track(Road Atlanta) is a much better playground for high HP cars. I drove a friends C6Z06 on that track recently and while I loved the my M, I have to push it much harder to keep up pace which most certainly increases wear. In the Z I could short shift at 5k rpm and pass cars left and right. In the M that would require 7K+ rpm shifts in every gear, every time, and your right foot planted at every oppurtunity.
I think everyone here has made excellent points. I also agree with statements regarding repairs vs. track time. I'm willing to bet Z will be cheaper in the long run if track time is a factor.
Well maybe if you don't count tires.
