I rent the Camaro's from time to time.
My impression:
I initially hated the Camaro. It had a high "waistline" and a low roof. Making the driver (me) feel like I'm sitting in a deep bathtub. The car also felt heavy and large for a "sports car", the cheezy instrument panel did not help, and the automatic was as non responsive as humanly possible. Always in a gear too high. Manual shifting does not help, as most of the time it simply refuses to shift when asked and waits 2 seconds.
However, after living with it for a while, I came to appreciate and actually like/enjoy the Camaro. It was comfortable, quiet enough, quite capable handling and achieved fantastic fuel economy on the highway. (I drove it like an old lady in an attempt at maximum mpg)
I especially liked the suspension on rural roads. It was capable of absorbing bumps in corners without feeling like it was upsetting the car. (unlike some Mustangs with the live axle) And, I found the large bucket seats a very comfortable place to be for hours on end.
It's not likely I'd purchase one. But, that's only because I don't want a 4000 pound sports car. On second thought, maybe I will look into one.
The Cayman/Boxster cars are perfect right from the start. Fast enough, super responsive, excellent powerful brakes, and comfortable seating. If I were to choose between the two, I'd pick the Porsche first. Even a bottom of the line Cayman is super fun to drive, and quite a good performer.