.22 or nothing
By way of background, my daily carry piece is either a G21SF or an LCR .357.
This question probably falls well outside the normal realm of data you typically acquire on cartridge effectiveness. Some friends and I have discussed the theoretical scenario where a person has nothing but a .22 Rimfire handgun to use in a self-defense encounter against a perpetrator. Have you come across any data about how effective a hollow-point .22 round would work vs. one with a round nose? There's the notion that perhaps the hollow-point would expand and perhaps not provide sufficient penetration.