The German car magazine Auto Bild has made a comparsion video with a versus between the Porsche Carrera GT and the 2011 Porsche 911 GT2 RS. Race legend Walter Rohrl takes the Carrera GT around the track against the fastest production Porsche ever to be developed, the GT2 RS.
6 minutes of my life wasted, i dont speak german, and there was no race or such
To summarize:
Carrera GT is a race car which they changed to be allowed on the road. GT2 RS is a road car thats made real fast.
The GT2 RS is faster simply because its 10 years younger.