You don't always need to use the handbrake to get a spin/slide, cars like the Sagaris in PGR3 would slide under power if you just had some decent lock on, I remember purposely fishtailing it along straights with just constant on/off throttle/steering to keep the kudos going up..
I'm picking my PGR4 up lunch time and will see if it's any better then PGR3 on the wheel for myself..
after Forza 2, I am a big fan of the wheel, the 'finesse' of control seems to work better then being able to go lock to lock quickly for me.. it took some practise, but I think I've got it relatively nailed..