Which GLI would are you considering, the 24v vr6 (02.5-04) or the 1.8t (04.5-05)?
I had a 24v 03 GLI, it was a great daily driver in my opinion, but not much more than that. The 1.8t is a nice car too, but no any better than the VR6 model. If I had to choose between a GTI and a GLI, I would choose a GTI.