I'm a hard core 1911 fan, but I know some of my readers like the Glock. It really comes down to preference (like your brand of car), and it usually makes for a great debate around a camp fire. I've always admired the Glock for the space age polymer frame, and all those crazy torture tests that were conducted on the Glock. According to the vid, some of those tests might be BS.
As a quick side note to the d-bags who created the vid. If you let folks embed your crappy long video, far more people will actually watch you conduct unsafe firearms tests. Sorry kids, but you can only watch the unsafe vid directly at youtube.
The vid is pretty long, but the gist of it comes down to the lack of performance after being dumped in water. I don't think casually flipping your Glock into a fermenting puddle is a safe or good idea. Hell, a 5 gallon bucket would have done the job just fine for soaking purposes. When the derp sits in the turd-cuzzi, he seems to be directly firing at his feet. I have no idea how much force the bullet loses under water, but I would imagine it could still do some damage at such close range.
I guess it was interesting that the Glock didn't fire all that well after taking a swim, but I don't really think you'll take your Glock underwater zombie hunting. I found a different derp who conducted a similar test in his swimming pool with a 1911 in the vid below. You can fast forward through him swearing and acting a fool to about one minute in to see the underwater firing. Impressive? Nah, I'm still not convinced I'll ever have a need to take consecutive shots underwater at zombies....