Which model years are you looking at?
There is both an old and new GTI 1.8T engine, and old/new Civic Si bodystyle and engine.
The first 1.8T (came out in 2000) had 150hp and 155 lb-ft of torque; the updated 1.8T has 180hp and 173 lb-ft of torque.
The late 1990's Civic Si coupe was a 1.6L, NA car with 165hp and only 111 lb-ft of torque (less than my Golf GL
), although the new Si hatch got bumped up to 2.0L with 132 lb-ft (but same hp).
So, by comparison, the GTI 1.8T is definately faster (and dare I say more refined) stock. The Honda would rev well in the high range though, and if you slapped a turbo onto an Si, as well as the usual bolt-ons, I'd think it could be faster than the GTI ... probably lighter than those husky mk4s too.
Everyone else here is probably strictly Euro, I would be too except I used to drive Hondas in high school, so I still respect them - especially the Si.
