I have two Glock MOS pistols: 19 and 34. One has the Trijicon RMR and the other the Vortex Venom.
Both are zeroed for me at 25 yards.
However, I just plugged in the data through one of my ballistic apps, iSnipe. I found that at a 10-yard-zero, the point of impact is +2.5 inches at 50 yards and -2.7 inches at 100 yards. My own experience is that at a 25-yard zero, it drops about an inch at 50 but 9 inches at 100 yards. When I ran it in the app, it was pretty much where I tested it to be. When zeroed at 15 yards, the calculation came to be a drop of half an inch at 50 yards and almost 3 inches at 100.
Seems like a 10 yard zero is the most optimal distance for zeroing a sight for a 9mm.