I own both a Kimber SS Full Size 1911, and several Glocks. If i were target shooting, my Kimber is more accurate, BUT, for self defense i would definitely prefer the Glock for several reasons.
First, as was already said, the Glock holds significantly more rounds, and i dont care what anyone says, more rounds is better no matter how you look at it. And its not one or 2 more, in .45 its 6 more (8 vs 14), a 9mm G17 holds 20 ROUNDS! with the +2 floorplate.
The Glock design is, IMO, inherrently more reliable than a 1911, 1911's have a rep for being picky about non FMJ ammo, Glocks eat up anything. Incidentally, i have a G17 that has at least 10,000 rounds through it, not ONE jam yet, not ONE. Wish i could say the same about the 1911's i have owned and shot.
Another great reason to choose the Glock is that is virtually rust proof. When FULLY disassembled (not just field stripped), i wash the frame and slide in the SINK, with warm water, dish soap and a toothbrush, it works perfectly and i have yet to see a speck of rust, try THAT with a 1911, yikes!
While both the 1911 and the Glock can be easily disassembled into its smallest parts, it takes less time with the Glock, and spare parts are DIRT cheap and easily replaced, not that youd ever really need to, the Glock is virtually indestructable. I have heard of G17s that have gone well over 100,000 rounds with no major parts failures, im not sure a 1911 could do that. Glock is one of the few guns i would buy used, they just dont wear out.
I guess the final reason is that a Glock is a bit cheaper than a quality 1911.
I keep a G17 near me at all times, yes, its JUST a 9mm, but its 20 ROUNDS of it, and the G17 is so easy to shoot accurately and quickly, i can put all 20 in the size of a fist at 21 feet in about 5 seconds.