Hum, I must turn that round, my 3200 manual was savage acceleration in a straight line.....right up until you hit the bend at the end of the straight then it was sort of "brown trousers" time.
Round a track the 4200 would dispense with the 3200 I feel....AC, I can't comment as I have never driven one.
The balance of the trans axle at the back makes them light years apart in the corners.....albeit the 3200 may well do the 4200 in a straight line.
If I had my time again, I would still buy a 3200 first then progress to a GS.