Again... in GT4... you could feel the difference between an Acura RSX and a Honda Integra... and it wasn't just the weight... you could feel the difference in tire grip and suspension calibration....
Correction: you could. I couldn't feel any difference between 1980-th RUF and Impreza. 95% of GT4 cars feels like same car with different acceleration and braking (and model of course).
The game was really bad. Physics were poor even in comparison with non simulator racers like PGR and NFS 5. AI was the worst I've ever seen in racing games. Racing events sucked because of all this strange rolling starts and random opponent's cars.
There is no comparison between GT4 and GT5 Prologue