i think it would be closer than you think, acceleration wise, yeah the sti wins hands down, but on a track, mountain road, autocross, etc.. the e46 would be very close. ive seen STIs get run down by some pretty unexpected cars on track days, a stock engine miata, on coilovers and good street tires. a mostly stock engine e30 with springs and track tires. i was actually riding in my friends sti when the e30 destroyed him, and while he's not an amazing driver he was pretty damn close to the limit of his car. STI's just push wayyy too much, and it really does effect their track performance when your 10 MPH down coming out of every corner.
e46's are probably my least favorite gen of 3 series though, id take an e30 any day. though the ZHP is badass, and probably one of my favorite bmws.