My second handgun was, and still is, a Glock 21C full frame compensated .45 ACP. I chose it because Glocks are simple (I can completely dis-assemble and reassemble with no formal training), utterly reliable, and needs almost no upkeep. The pistol is more accurate than I am (center mass is no problem with it), will eat anything, and has only jammed for me when I intentionally limp-wristed it to see if I could cause a misfire. Although it is fine out of the box I did add a plug for the grip, a captured steel recoil rod and spring, and a 3.5 lb. trigger bar. It may not have the history of a 1911 but it had all of the features I look for in a handgun, my only other handgun at the moment is a Makarov which shares many of the same traits.
Even though the .45 ACP is only slightly larger than the 9MM it has considerably more stopping power, personally I'll take slow and fat over small and fast when dealing with a handgun. Just adding my $0.02.