well .. it's a fact that Forza 3 has an awesome driving sim.
I have also heard the xbox360 has a better texture pipeline, can use larger/more textures (it really shows in side-by-side comparisons of Dragon Age:Origins)
Thing about Forza is .. once you go thru an get the 280Z(Fairlady) all set up .. ooo .. then you can setup that Ford GT40, ..and the Datsun 510 is just a *hoot* to drive with a few tweaks .. then there's the dual-turbo'd civic hatchback with rear wheel drive conversion ..220mph down the Mulsanne in a *beer can* .. ROFL.. and soo many others.
I even have the '69 Dodge Charger, 540 Hemi, setup for road racing ..and it does a pretty good job for a battleship in the S-class (romps on Ferrarri's, Vettes, an the like)
Don't get me wrong, I love the late model Z06 I have setup for that same S-class, and it's easier to drive . . but the Charger is fun, too.
There are so many fun cars

.. the baby blue ZR-1 Vette (aluminum L-88) is a blast too.
-GE aka Frank