I can't speak for the 2007 Porsche 911, but I did some research on a 2008 Cayman S. I only drive my Z about 6000 miles a year (I prefer my Yamaha FZ8). Here's what I found out; the Porsche is cheaper!
- With Geico, my insurance is $350 less, yearly.
- Factory recommended maintenance intervals at dealers in the DC area, about $1000 less over five years.
- Resell value higher by more than 10%.
- Better (real world) gas mileage.
- Longer factory and extended warranty.
Unscheduled repairs would be the wildcard, I suppose. Doesn't matter anyway, my wife totally vetoed the idea
.