Of course Forza 3 beats GT5 on a lot of features. The user generated content, the damage / physics stuff, the way it will be integrated in Xbox Live etc.
I don't know why people are hating Turn10. Both Forza games were AAA games so far and Forza 3 won't be different.
The latest GT received a 75 @ metacritic.com
Turn10 is just one great developer and they delievered. Just check the demo.
Imagine not having GamePass on your console...