I've been reading the Ayoob files. Mas does a good job of looking at all angles of the gunfight experience. He addresses knockdown and the psychological effects of being hit, including the phenomena of people going down when they thought they were hit. They could feel the bullet, the burn, and then often collapsed. We're talking people that were not actually hit. Some people are shot with a .32, and others with a .45. Some go down with one shot from a .32, others take several rounds from the .45 and keep coming. Excepting the central nevous system disabling shot the psychy of the one being shot has a lot of influence on how soon he or she goes down.
Still....the bigger, harder hitting, deeper prenetrating rounds, will no doubt see a person "put down" quicker, with the same placement, than those of a lighter caliber.