I had this same choice and went the 34gtt - 33 was never an option as I hate the body styling.
In regards to the 34 (briefly):
Pro's
- Newer car, less age-related issues
- Less driving wheels is less stuff to break
- More unique vehicle
- Nicer interior
Con's
- GTR is my dream car (34GTR anyway, 32GTR is my dream weekend track baby)
- Performance, sheer thrill of driving a race-bred vehicle as a daily
- Parts are easier to get than the newer 34gtt
Anyways, at least you're in a good enough position to be making the choice!
My dream is to own a 34GTR by 2008, the GTT will be my baby til then