I'm going to be one of the minorities and go with the Turbo. It's an easier car to live with day while still providing sheer driving pleasure... oh wait wrong slogan

I choose GT3.

Any of the three is a brilliant car, but I'd take GT3 because in every test I've seen it was described as the most fun, most balanced and involving.
It has the most linear engine, this car puts the driver in the main role, therefore it is the best 911.

I've read a review in Italian car mag (Italian ver. of TopGear) of these 3 cars. They say Turbo is the best only as a daily driver, GT2 is special car (super fast, surprisingly easy to drive, behaves extremly good in curves) but still suffers from a certain turbo-lag. Although GT2 is the fastest, GT3 wins.

BTW, Martin thanks for your great explanations! I always learn sth new!