Do a Google search for "Strasbourg Tests". In that test several European police agencies did a test on live French Alpine goats of the same size and weight of the average human male to see which cartridge disabled a healthy goat in the shortest length of time. I think something like 600 goats were shot in the thorax with various popular handgun rounds, and the time interval between the shot and the animal's collapse was recorded to the tenth of a second and averaged out over a series of shots from each cartridge.
IIRC the .45acp did very well, but it wasn't the top "stopper". Again, IIRC, the .357 mag firing a 125 grain hollow point round took the top spot. Also IIRC, the 9mm came in with a very respectable score, not far behind the .45acp in fact.
For me personally I usually carry a Taurus medium frame 2-1/2" .357 revolver in a Don Hume belt slide holster, except in hot weather when I can't conceal it under a jacket or coat. In hot weather I have been carrying a commercial Russian Makarov .380 semiauto loaded with Federal HydroShok cartridges in a pocket holster, but I am planning to upgrade to a 9mm Springfield Armory XD Compact semiauto before summer weather returns. IMHO the .380 is just barely adequate for self defense, but at the time I bought it there were no truly small 9mm guns on the market and it was better than the little .32s.
If I were you I would check out the Springfield compact. It has everything going for it that the Glock model 26 has and it's quite a bit less expensive. Although I really like the old .45acp and have owned several 1911s and one S&W .45acp revolver, I believe anyone is quite well armed carrying a reliable 9mm loaded with good hollow point cartridges such as Corbons or Hydroshoks.
It is also available now in .40 S&W caliber, but I wouldn't recommend such a lightweight (20 ounce) .40 caliber pistol to anyone who isn't quite familiar with heavy recoiling handguns. A 20 ounce pistol firing a 165 grain bullet at over 1100 fps is going to kick pretty darn hard, and if you aren't accustomed to that kind of recoil it can easily develop a bad flinching habit which ruins your accuracy and is very hard to overcome.
I know about flinching, because a Colt Lightweight Officer's Model .45acp caused me to acquire a flinch habit which I'm still bothered by at times. OTOH, I really enjoy shooting a heavy 8-3/8" Colt Anaconda .44 magnum, and it has no tendency to cause a flinch even though it's much more powerful than the .45. Little guns in big calibers are designed to carry a lot and shoot a little. But you need to practice regularly, and if your gun hurts you when you shoot it you won't practice enough.