They are both good guns, but I would take a Glock over a 1911. I do not like the two-piece feed ramps on 1911's, their extractors that need to be "tuned" and therefore go out of tune, or their grip safeties. However, with the right ammo, and a good gun, they'll run for a long time.
No matter which gun you get, buy a good holster to carry it. Not only will it make carrying more comfortable, but it will make it safer. The Glock has no external safeties, so if you pull the trigger (or snag it on the wheelchair, your pants, a key, etc) it goes bang.
Do not get a compact Glock in .40 or .357 Sig if you plan to shoot it much. Those calibers beat up the little guns. Well, get it if you want to, but expect more frequent parts breakage (in the 5,000-8,000 rounds range).
While I don't know the specifics of dealing with a wheelchair on a daily basis, I wouldn't think that concealment would be a problem. If the weight of the gun is not a problem, get a big gun. They're easier to control and less punishing to shoot. They even come with a higher magazine capacity. Heck, if I was in a wheelchair every day, I'd find a way to conceal a shotgun. Stashing reloads seems easy too. Do it if you can.