Been there done that. I used to play the game a lot, but it got REAL boring, REAL quick. I made a few videos I posted up here a while ago.
Using the G25 in both, all assists off. N3 tires all around in the drifting video, and S2 tires for the hot lap.
I played the game the way it was supposed to be played. The online, customization, tuning, and a load of other things kept me going back to forza 2. Now that Forza 3 has launched I see no reason to play GT other than being able to use my G25 which was awesome.