I've seen a number of different sights for Glocks
Personally, I think the fiber optic sights are the easiest to use but the least reliable/flimsy as hell. I had Truglo fiber optics and I couldn't miss with those things, the giant green dots even during a bright day, where so easy to use. However, the front sight filament fell out of them. They repaired it free, and it happened again. I got a refund. I was shooting during hot days and thats how it came loose, so I won't trust my life to them.
I prefer the three dot system. Trijicon makes very high quality night sights using the three dot system and the front dot is very easy to use (big). They're expensive. I use the Metropolitan 3 dots that are identicle to the trijicons and work just as well, the only difference is the front dot isn't as big and it's pretty much the same as the rear dots. They're cheaper.
My brother uses a one dot night sight, the front dot only glows and the rear has no dots. It takes getting used to and in my opinion it isn't anywhere as good as 3 dots/standard sights for fast target aquisition