Whatever you do... Don't buy a SKYLINE!!!!!!!!!
j/k
series 2 looks more agressive, i think thats about it. It came in 97 and 98. Personally i like the series 1.
The r32's a mad car, fun to drive, great on boost, but sluggish off boost. S14 is a bit better off boost, but it's more of a street car in that it lacks the extra sporty benefits of the r32 like stock boost and oil pressure guage, less adjustability in the seats and steering column, and a different suspension setup.
both good cars, S14 is newer, slightly safer option with service books, parts, etc..
Skylines go hard