I had this decision, built 32R, lightly modedd 33R or lightly moded 34T and went the 34 gt-t due to age and the fact its still a quick cruiser.
I can say in terms of grip the 33 gtr is amazing! Whilst the 32 gtr isn't far behind (older diffs, slower computers etc) and is slightly quicker down the 1/4.
Im happy with the choice i made, but if you want a real fast car you can't really go past a gtr, its got grip (more than a gt-t will ever know) and more power to it, it just feels alittle bit less chuckable, but you take a corner and your like wow did it just do that corner that easy.. least thats the impression ive had in the gtr's ive been in (decent tires/suspension etc).
Id probably lean to a 32 gtr thats had alot of money spent on it if i was you, just so in future you don't have ALL of the costs or the 34 gt-t if you want some more comfort to cruise with.
Btw if you search there's alot of comparison threads going around, i know i posted in a few of them! hehe