Buy something you'll love driving. I would go straight to the newest model you can afford.
Both cars are very quick, the GT-R will tend to scull your money a lot quicker though.
A mate bought an Evo8 today, I took it for a spin. Surprisingly good car, I did not expect the build quality to be that good. Very quick of course, off the mark (so out of corners) it is a machine. I can imagine it being easier to drive (so generally quicker). It would be very interesting to drive it on a track.
Just remember, if you decide on the GT-R, you'll have to treat it as a RWD that has the ability to pull itself straight. The R32's ATTESSA is pretty slow so you can get some good, easily controllable angles hahaha.
After driving said mate's Evo and then jumping straight into my car, I wish I bought an R33 for the better build quality . Sitting in an R32 feels like a sports car, whereas R33/R34 and Evos feel more taxi-spec. I'm glad I bought the 32R though. You have to decide whether to buy it on logic/reasoning (Evo) or on emotion (GT-R).