That's a really tough question to answer since they're such different cars. Also, I'm still breaking in the STI, so I haven't taken it over 4k RPM yet.

I can say the S2k is much more raw...the steering and throttle input is just so crisp and satisfying. The seating position is better and I just love the overall feel of the car, especially after the turbo install. The car is just incredibly fun to drive.

The STI is much more refined and the grip is just awesome. Before tonight I would have said my S2k feels quicker, but I flashed the STI to Stage 1 software and in S# mode, it is VERY quick. For the first time since I've owned the STI, it put a huge smile on my face.