I have both Rfactor, GTR2 (based on Rfactor engine) and Live for Speed and I have to say LFS has the most accurate physics of any racing simulator. I swear my times at autocross are faster because of that game! You can actually watch the tires deform and the contact patch change during turns and such. Rfactor has much better graphics though and WAY more mods, cars, tracks and such. Really though, playing Live for Speed with a Logitech G25 is the closest thing to real life that I have experienced on a PC.