The army did a study around WW1 of all different pistol cartridges, even explosive ones, and they found that shot placement was more important than caliber. According to them the only way to put down an opponent and have him stay down was to shoot him in the brain, the spine or the long bones of the legs. That doesn’t mean your opponent won’t die if you shoot him somewhere else it just means they can retaliate before they do. Just as a miss with a .45 is the same as a miss with a 9mm a .22 in the brain is going to stop them as well as a .45. They also agreed with your long gun strategy with the shock created by a rifle bullet’s velocity having amazing stopping power.
People have mentioned a shot in the heart. While that will kill, it won’t stop the determined. We had a great cop in my church. Phoenix office John Hobbes. He was shot through the heart and still got off a full mag killing the felon AFTER being shot through the heart. The details weren’t reported in every news article, but I took by CCL with a fellow officer who had just retired and he explained it in detail.