I have a theory on this PiotrB and I don't know if it's correct or I'm totally off. But I believe the classic cars (250 TR / LM / GTO and even the 365) are comparatively easier to drive and control with a wheel vs the Sixaxis. Maybe that's the wrong way to put it--I don't know if it's easier with the wheel. But I really do believe that this game, under certain circumstances, favors sixaxis drivers. But this advantage is negated with the above mentioned cars.
I notice, for example, that my lap times in the classic cars are much more competitive than they are with say, the F430 vs people who drive with the controller.
Maybe it's just 'wishful thinking' on my part but I see more and more evidence of this.
Incidentally, I hope you'll take part in the 250 GTO event this weekend.