I own roughly 15 different firearms of various configurations and cablibers. Of all of them, my Glock 21 is my favorite. For me, it is an absolutely perfect fit.
I can get chest hits on silhouette targets out to 50 yards with it (never tried beyong that) every single time. That's obviously not target competition quality, but I've found it to be far more than just "combat accurate" (to borrow a term).
Followup shots are a dream come true. Shooting IDPA, I've gotten to where I can put two shots into each of three targets at about 10 feet in roughly two seconds. That's from holstered to the last shot being fired. Double taps are just sweet.
The one drawback to the G21 in general is actually a plus for me, and that's the overall size of the gun. I'm a pretty big fellow (6'3, size 14 ring), so having a lot of gun to hang on to is a GOOD thing in my book.
The trigger on the Glock is going to disappoint you if you're a serious 1911 shooter. Because I never was, I had no preconceived notions to overcome. Also, I had the 3.5 pound disconnect installed in my gun by a Glock armorer buddy of mine. Not sure if it makes a LOT of difference (I never even fired it with the standard trigger disconnect in it), but the package I have right now suits me to a tee.
Also, the grip angle on the Glock is pretty different from most other firearms. If you hold your wrist at the same angle with a Glock as you do your 1911, you'll end up with the barrel about 10 degrees high. For me, they point naturally.
Capacity is where the G21 generally excels over most other .45's. Obviously, 10-rounders are shipped with the pistols, and 13-rounders can be had, but for the price of just a handful of them you could buy another pistol. That's a two or three round advantage over most 1911's with the 10-rounders, and almost twice the capacity if you pony up for the 13's.
As far as reliability goes, I have something in the neighborhood of 1500-1800 rounds through mine and it has never, not once, failed to perform. No malfunctions of any kind.
Because of the mass of the gun, and the low bore axis, recoil and muzzle flip are negligible IMO.
Okay, I'm done!