It depends on what your after. If you want all out performance and handling then the GTR is a clear winner. But if you want a good looking daily that has decent power and is fun then a 34 is the go.
A GTR will always be more expensive to repair and insure and its always going to be a thief magnet.
Its a hard decision, I'm kinda going through the same thing now, do i get a r32 gtr, a cheaper r33 gtst, or a newer 34 gtt. If only i was rich i would have them all .
I wouldn't buy a GTR unless it had a rebuilt motor though, I'd say 90% of original motors still running have done 200,000km's plus, and just the thought of having to spend mega $$$ on a rebuild is enough to turn me of one.