Hi. I went thorugh this decision about 7 months ago. I came really close to buying a gts-t, but ended up going for a 98 gt-t instead. Here's my decision process:
I personally think the R34 is a better looking car
More refined feel compared to the R33
206kw Neo engine versus 187kw S2 motor. Torque is also up ~50nm. Very responsive and plenty of torque down low.
Slightly newer car, hence less likely to experience problems
Price difference, i thought i would fork out the extra $6k for the 34
Revised interior
Less of them on the road, R33s are becoming way too common for my liking
It's going to come down to gut instinct. When you find the right car, you will know. I looked at around 6 cars and knew straight away that the 34 I have now was for me. What ever you do, don't buy the first car you look at. Take your time to drive other cars, see how they differ.
7 months later and i still love the thing to bits. I look forward to driving it everyday.
Best of luck my friend