Both the factory Glock and the Meprolights (may actually be/probably are, the same sights) have a pretty narrow gap on either side. I have them on most of my Glocks, and would actually prefer a more narrow front sight giving a larger gap.
I tried to take a couple of pics, but what the camera shows, isnt what I see when the gun is held at arms length. And thats even when the camera is held back.
I would prefer a gap something like you see in WVsig's pic, but at arms length, and thats what the camera shows, but its not what I see when actually shooting the gun. The gap is considerably smaller/finer, which makes for a slower to acquire sight picture. I actually just use the dots from about 10 yards and in, and dont start transitioning into a traditional sight picture until further away.
I prefer the three dot night sights and have used/tried a couple of different makes. The "all green" Meprolights for me, seems to be the biggest, brightest, and easiest seen (they have a nice, bright white ring around the vials). If they would just open up the notch in the rear sight, things would be about perfect.