I received my Fanatec wheel 4 days ago. So I throwed away the MS crap wheel and installed the Fanatec on my old Playseat. It's really perfect in both games ! The gearbox is way better than the one on the G25.
I compared the Nissan 350Z RS in GT5P with a tuned 350Z in FM3 on Suzuka.
IRL, I own a tuned 350Z I frequently use during track days (Nürburgring, Spa and some tracks in France like Dijon Prenois). I tried to tune the 350Z in FM3 as close as possible as my real car.
Yes, the avatar is a simulation too
I used both games with no driving help except ABS, manual gearbox, manual clutch, right foot braking with heel & toe.
If you drive beyond the limit, both games feels very similar except the car in FM3 does not feel as connected to the road as it is in GT5P.
If you try to go faster, the Z in GT5P will violently oversteer and it is very difficult to catch. Not realistic at all compared to my real Z which is very progressive and a pleasure to drift. (the stock Z in GT5P has the same problem).
In FM3, the Z is progressive at the limit and easy to drift. A lot closer to the real one !
My conclusion : a better sim would feel like the car in GT5P and react like the car in FM3 !
I hope that GT5 final will be this sim !
By the way, I did not played GT5P for months. I did not remember how bad it sounds