The R33 is an evolved R32. They moved the tank back to give a better weight distribution, and made it very slightly longer.
The R34 is the 'playstation generations' Skyline w/ traction control etc.
I like the look of the R34, but the R32 looks a bit dated now and not in a 'timeless' way. The 33 shape is probably a bit more of a 'neutral' design so it has not dated like the 32. I wouldn't say with the 33 vs 34 shape one is better than the other.