oh man - your opening a massive can of worms. I genuinely believe it's a personal preference thing.
I'm currently trying to buy myself a trackmule gtr as well, because I believe the awd will reap me quicker lap times, but there's a miriad of reasons whhy either would be better. I guess it comes down to driving style, budget, suspension setup and power, as well as a million other reasons. There are heaps of rwd purists out there who lap quicker then awd cars, I guess thats proof enough that rwd's can be just as quick as gtr's, but then again if you're watching skyline's race on tv and stuff you only tend to see gtr's (obviously for another good reason too)
It's up to your own preference.