I've tried the Z4 GT3 at Brno and I couldn't be less impressed. No feeling at all, it is too easy to drive, feel very arcadish.
Then tried the BAC Mono at Oschersleben (dry track but everything else wet), and it is nice too se how the grip improves after some laps due to tire heat, but it felt too slippery all the time, and again too easy to just control the slides of the back.
On the other side, playing at 35~ fps is not the ideal scenario to judge the physics :/