The Glock 40's have been known to blow up. Seriously. It mostly happens with re-loads, though. Do a google search on "Glock" and "kB!".

I tend to like 9mm because it is easer to get, and the cheapest center-fire round available. Less cost = more shooting. But .40 does have more power. 9mm is no slouch either, if you use modern hollow-point ammo.

Is there any reason that you are sold on Glock? I kind of dislike the total absence of any real safety (the little trigger lever does not really count). I like something with a manual and/or a grip safety. I have a Springfield XD, and the grip safety is nice.