The best way to describe an atb diff on a 4wd is just to say the diff will pull the car harder around the corner with the back end pushing the car. Means even more cornering grip and a more balanced, less understeery feel.
Tbh I would always go for the peloquins atb diff in the high torque version. The quaife doesn't kick in as hard or fast. The quaife also doesn't come with new bearings which are 130 quid and not available through VW!
I had a little play in the Apr golf R last night. Had one shot at a launch and managed a 3.7 to 60, then 8 to 100. They still have a few things to fettle with, but that turbo setup spools faster than a k04. Plant the throttle and boost is there in an instant.