Three great choices, I've shot and owned [and sold, and bought again] all three a few times over since 1990 (including the SIG P225 and Glock 22 if that adds anything). Like many others have stated, you'll only be able to determine the best for you after trying out each of the three and see what feels/works best for you. That said, I rate the P226 on top of the podium with the Glock at second and the Beretta taking third. The P226's function, fit and trigger pull, for me, are head and shoulders above the rest, with trigger pull being the most important in my book. In MY experience, it's also the most accurate of the three. Never had any reliability issues with it. Ever. I've used the P226 in competition and never worried about gritty trigger pulls, stovepipes or other function issues. Consistently flawless! The Glock is also a worry-free service pistol that has always been stellar for me in the reliability category, and I've also been pleasantly surprised of its accuracy. I have no issues with the striker-based trigger pull, but I can see how some people wouldn't like it so much; again, it's a personal preference thing. If it means anything, my Glock 17 is my go-to pistol for CQB matches. Of all three, it's the easiest to use (mag changes and drawing from a holster) and I prefer its ergonomics over the others. Much like a CZ-75, the barrel is lower in the frame and closer to your hand which reduces recoil flip. The Glock 17, in my book, is a good-to-go and all around top-shelf pistol! The Beretta 92, while by far the best looking of all three, has that less-than-stellar late 80s type Wonder Nine SA/DA trigger which, to me, is its liability. I also agree with previous statements that the ergonomics of the grip may not be convenient for guys with smaller hands. In my book, based on my experience, they are not quite as accurate as the P226 and the Glock 17. Again, experience may vary between pistols and shooters, but the Beretta never did it for me beyond the esthetic department.
At any rate, try them all out, get what's best for ya, and good shootin'!!!