I purchased the LCE FM4, ended up selling xbox and going back to gt5. then bought another xbox, and forza again. Plenty of Iracing thrown in also, as well as the other PC sims (rfactor/rfactor2beta/gtr2/evo/LFS/NetKarPro....list goes on. I'm a t500rs wheel th8 shifter user and have a great deal of fun when i play these games. sadly though, can't report on the forza physics with a wheel. i refuse to buy fanatec gear, when i have a G25 & T500. xbox failed big time with the 360 wheel support.
as was stated by someone earlier, if you take a stock car in GT5 and downgrade the tires 1to 2 compounds, you've got yourself a very accurate physics representation of RL. That being said, GT5 acts nothing like real life when you don't drive the cars the way they're intended to be driven. i.e. if you dive bomb a corner you can often power through without much risk...in Iracing, you'll spin that thing around 7/10 times. same goes for off track recovery, or any type of recovery for that matter. The other console disappointment, that GT can't shake either is the net code..not the best in the world.
GT5 is, IMO, the most fun driver on the market, and I think their physics are worthy of 10/10 if being rated against all things console. 7/10, considering the pc market. Forza...5/10. I love all aformentioned titles though