Ive just bought series 2 R33 and Id have to say that its a much more appealing package.
The trim inside the car is better, the headlights are much better, they are newish design. The steering wheel is nicer.
Two air bags, series 1 has one.
Also its safe to say that more series 1s have been boosted and thrashed compared to series 2.
In the end II will cost a few grand more than 1... I much prefered the look and feel of II so i got one.