Penetration kills.
The only thing that incapacitates instantly is an upper CNS hit. Beyond that a hit to a major blood bearing organ (heart, liver or kidneys) or major bloodvessels is the only thing that is going to stop a human in a short time frame.
"Stopping power", "knock down power", "energy dumping" and all that other crap is a myth.
Its not even a question of big and slow vs light and fast. It is a question of, can my bullet go through clothing, skin, fat, muscle and bone to hit the important things?
The truth is, all pistol rounds are just about the same. A FMJ 9x19mm round will penetrate deep enough to hit vital organs. A FMJ .45ACP round will penetrate deep enough to hit vital organs. Bullet diameter plays a slight role here, but it should be a secondary thought. A larger diameter bullet hits what a smaller diameter one barely misses. With larger rounds comes more recoil. Two rounds of a smaller bullet diameter gives a higher vital hit chance that one round in the same timeframe with a larger bullet diameter.
The usefulness of JHP is questionable too. They don't expand all the time in tissue. When they do, it leads to decreased penetration (the most important factor), but a larger permanent wound channel. This may lead to faster blood loss, and a very slight increase of a chance of hitting a vital area. It seems that JHP may also decrease certain firearms reliability. I do not think the trade off of a larger perm wound is worth the decrease in penetration and reliability. I would choose FMJ.
So what to pick? The round with that largest unexpanded bullet diameter that you can continuously dump out rounds where recoil and muzzle flip wont slow you down at all. The higher the capacity the better, use FMJ rounds.