335 is asking R32 GTST vs S14/15, not S13.
R32 is 10 years older then S15, its still a bit bigger and heavier, but less power.
the good of R32 is front and rear double independent double wishbone suspension, 6 cylinder engine, and you can drop RB25 or RB26 or even RB30. This is what S15 require more work on it. If you are mod monster and don't mind the age of car, R32 is better, because you saved the price difference in your pocket for new gear.
If you like newer car, S15 no question on it(you can get R34 if you want newer and bigger).