I've owned 2 996's one a C4 6 spd and a C4S Auto.
I had a new GT auto for 6 days on vacation. The new GT is just as powerful and better riding in every day use. The shift paddles and steering wheel controls on the GT are quirky in comparison. The seats in the GT are every bit as good. The view from the seat gives you the impression there is a slight rise in the front hood going forward. I suspect that on the track, the non-track pack GT would seem softer and less capable., but you'd have to test that. All in all its a good car and in every day street use would keep pace with any non turbo or non GT3 996 and 997's I would bet. The auto was pretty good. My sense is that the Porsche brakes would win the stopping test.