Of course the 996 Turbo is faster, especially in the higher speed range. At speeds above 200 kph, weight doesn't really count anymore, what counts are torque and power figures.
And the 996 Turbo has plenty of it.
The only domain where the 997 Carrera S might be quicker is on little country roads with lots of twists and turns because the 20 mm chassis is just unbelievable and the 996 Turbo still tends to understeer a little bit and the turbo lag is also a point. But it also always depends on the driver.
On the Autobahn however, the 997 Carrera S stands no chance against a 996 Turbo with manual, not to speak about X50.
This was one reason why I went for the 997 Carrera S, I don't use it as a daily driver and I won't drive it too much on the Autobahn. It is more of a fun car for my spare time.
I could have bought the GT3 at my dealer for the same purpose but no rear seats, more insurance cost and lacking PSM (right, on the street PSM can come in very handy). Price tag was the same on both cars.
As a daily driver, I would probably choose the Cayenne Turbo
but for fun, right now the 997 Carrera S is the closest thing to a GT3 without giving away too much safety and it has the more modern look too.
When the 997 Turbo shows up, I might change my mind and go for the Turbo but right now I'm so happy with my 997 Carrera S, I can't really put it in words. I mean you drive this little baby in a long but sharp curve and you get faster and faster and you wonder when the tires are gonna loose grip and you're waiting for that power slide and nothing happens. Unbelievable stabiliy and the new Michelin Pilot Sport 2 tires seem to be stickier than ever.
What can I say: right now I'm in Porsche heaven, a Cayenne Turbo as a daily driver and a 997 Carrera S as a fun car.
If I win the lottery, I get a Carrera GT too.