That all depends on the mod and who programmed the physics etc.
rFactors only real probs are the handling of turbo spool/lag and a lack of a Starlet GT race series
I can't drift that well in it but I would probably spend 90% of the time off the track IRL anyway
As for V8sc, I liked it initially but when I played online I found that you didn't actually need to brake for stuff and my careful efforts at racing line etc were simply not required.
GT4 I liked a lot but I didn't play it with a wheel and controller are haxx imo.
I am getting an Xbox for Forza 3 as I played it the other day and it. is. $$%. good.