who cares? neither of them are race cars so why even act like they are...
the Si will rape the VW on reliability and pretty much anything else involving you swearing the car out itself.
the VW will most likely be a better performer, esp for the $$$ minded aftermarket consumer, where the 2.0t engine has fewer limitations than the Si, esp under the $2k mark.
the GTi in the straight line will kill the Si, thats for sure, esp when outfitted with the DSG transmission. BUT the DSG is totally nauseating as it does not help with downshifts-- many even claim it can do nothing but hurt you on a track where you will be shifting neumerous times.
all in all i'd say if you are looking for a sensible daily driver go with the Si, if you are ONLY performance minded at all (as much as one can be in this segment) go with the GTI, just be weary of the DSG transmission.