I've run the TC3, cuda R2 and TC4. Out doors on tarmac, the R2 was the fastest, seemed alot easier to set up that the other cars. I haven't done much running with the TC4 out doors (BMI now), but when you get the setup right, it seems to fly also.
Indoors, I'd have to say the TC4 by miles, found it much faster and easier to drive as the grip came up. The drive train on the R2 however had much more "free spin", but the TC4 feels punchier on the track.
Cheers
Crashmaster