Caliber wars.... gotta love them simply because they never end. So I may as well jump in with my 2 pennies ...
Holes.... stopping a determined attacker is all about holes. Holes let blood leak out. Holes do damage to nerves and brain. Damage from holes physically incapacitate human beings.
Holes from big bullets do more damage than holes from small bullets.............. BUT!!!.............
Bullets that miss do not make holes regardless of what size they are.
What really matters is being able to control the gun well enough to put all the bullets, regardless of size, in a place that will make holes that cause the most damage.
For an extreme example.... one .45 that hits and makes a hole followed by several that miss equals a hole .45 of an inch (perhaps up to .75 with expansion). Yet 10 .22 hits that make holes equals a 2.2 inch hole.
Granted 10 .45's make a 4.5 inch hole but if the person can only control the .22 (or any other caliber) then the best caliber is............
......the caliber/gun combination that individual person is most accurate with (makes the most holes) under the stress of rapid fire while on the move.
Why rapid fire while on the move? Because real life is not like on the range where folks are standing still in a perfect stance carefully acquiring a perfect sight picture while gently squeezing the trigger shooting at a stationary target that isn't shooting back/trying to stab you. Real life is chaotic with lots of yelling, tunnel vision, bad guy moving around/attacking, while you are trying to move out of the way/get to cover/protect your loved one's, maybe in the dark while it is raining..... stuff that isn't anything like a sunny afternoon on the range with your buddies.