All I know is I like the gti because: It'll outrun the si civic with minimal mods, the gti isn't the top of the line for the golf body like the si is for the civic and the price reflects that, interior is much nicer and more refined, tq, responds better to mods, turbo>vtec, lsd, finally if you put equal money into both the gti will walk on the si, I'm not saying that the si isn't in the same class or an inferior car, but I'm confident that my gti will walk on most si's out there and including the cost of the car I've invested much less than 11k