i think the best comparison is when the gtst and silvia are in stock form. after my initial 1000km, my stock s15 chopped a stock r33 gtst (AIR4S1) in a quarter mile. the power to weight ratio was the deciding factor. even now with exhaust and airfilter, my s15 continue to surprise a lot of gts' and even GTRs!!!
....and when it comes to looks.....it's just personal preferences..although when i cruise with my skyline friends...the s15 draws more looks than my friend's R34 GT-T