Well, all I'm going to add to this conversation (before the Glock fanboys start rushing in) is that I've never shot an inaccurate-out-of-the-box Sig - they always seem to be well sighted in and shoot, for the most part to POA within reasonable distances. Same with HK, maybe even more so.
I have shot at least a dozen varieties of Glock, OOB and at least half of them usually shot noticeably low and to the left or high and to the right. I don't know if it's a byproduct of their manufacturing process, poor design, poor QC, or what, but that, coupled with the overall cheap feeling of the guns and awkward grip angle made me never want to own one of my own.
If you shoot the Glock and like it best though, don't let my experiences halt you from buying one. Lots of people REALLY like them. Buy what you like to shoot. I'm with Voodoo... I demand accuracy from my weapon, for shot placement is key. Accuracy, reliability, and to an extent "stopping power". I say to an extent because I would rather accurately shoot a home invader in the throat with a .38 than blast him with a .45 in the arm.