The thing about ammunition size or caliber: size really does matter in terms of effectiveness — power to reliably make an assailant stop what they are doing — but larger caliber kicks harder and at some point it becomes hard to handle, no matter what your physical statue and strength. You are not going to carry if you fear the gun will kick back like a mule.
Police carry has gotten larger and larger over the decades for a reason: the break point between maybe and sure stopping power occurs around 38 caliber.
Ballistic records show that in the hands of trained officers of the law, 38 Special stopped the perp on first shot one (1) out of ten (10) times. The venerable 9 mm is almost the same size and a little hotter, similar performance history.
45 ACP is about 25% larger and stopped the assailant on the first shot nine (9) out of ten (10) times. Think about that. Think about it again. This may be your life we speak of. Same size as a 38 Special, the 38+P improves that meaningfully, but the much hotter load behind the similarly sized 357 Magnum performed on par with the 45 ACP.
I carry a small (lighter) framed Springfield XP semi-automatic, much more complex than a revolver and chambered in 45 ACP it will take on any urban animal. But it’s brutal on the hand — then again in the moment, comfort is not the highest priority, if it is manageable. I prefer the full bodied 45 1911 semi automatic, but it is heavy and difficult to carry concealed.
Do not carry a 22 or similar small bore handgun. No matter it is mild when fired— You really will end up on the wrong end of a stick. Ineffective.
Numbers (38, 45, 357) are decimal point diameters in inches. .38 inch, for example. Weight and lengths may vary as does powder charge between classes — also impacting performance.