That all depends. Are you wanting a scope style...........
or holographic sight?

or holographic sight?

Thank you, I had this question as well. That is some good infromation to think about.Assuming that you are looking at a slide rider and not a frame mount. I have fired Glocks over various types with Bushnell fast fires, Trijicon, CMore, doc optics, Laurie, and other labeled brands of the micro sights on them.
The sights have been both mounted on plates fitted into the rear sight dovetail and machined into the slide itself. The advantages over frame mounts is the site is lower to the bore so you don't have to adjust your presentation to "hunt the dot" like you do with a frame mount. Biggest issues are the mount itself to the dovetail, they sometimes aren't so robust. The slide milling is best, brings the sight in line even more.
Bad thing is that since the sight is mounted to the slide you have a harder time tracking the dot and it tends to bounce more in your vision which slows your followup time some.
malladus
Check the rules for the events you plan on shooting in. Many times the dot will kick you into an open or unlimited class. Local club I shoot steel and USPSA like matches at, the dot kicks you into open class and then you are swimming with the full blown race guns.I would like to have it replace my rear sight. I plan on shooting at some local matches but, nothing too big. Just some weekend events. Don't want to drill the top even though I have heard good thing's from doing so.