If you want realism, there is one area on the PC that wins hands down: the modding scene. First you need to buy EA's F1 2002. Next go to
http://www.simbin.com/sbdt/ and read about their mods. Then download the amazingly superlative GT Racing 2002 and install. You will be able to customize so much your head will spin. They physics will be more realistic than in any other GT racer you have yet tried. Best of all the mod is free and F1 2002 is now dirt cheap. Enjoy!
p.s. wheel or gamepad strongly recommended.