good post Hybrid, Plus rep from me :)
you missed one thing though, GT physics suck, always have, and most probably always will (try drifting on GT4 with the DFP 900, its impossible unless you use stupid techniques, ie throw the car in at around 190, let it slip, then exit the turn doin 50)
the drift physics doesnt just count when ur drifting, if your racing and the back slips, you need a good physics engine to simulate it properly, the original Forza was bad in the drift area, you had to keep turning into the turn otherwise you would straighten up, basically, no countersteer required.
at the end of the day, im happy(read:EFFIN ECSTATIC) with FM2, GTHD might amuse some, but if there is even a hint of the GT4 physics it wont put a smile on my face
this post is opinion and not fact :p (although parts are fact)