I think the most important factor in choosing a firearm or cartridge for self defense is to understand why you are choosing it, understanding the benefits and understanding its liabilities. I have yet to see any real data, that analyses real-life defense outcomes that provides significant evidence that the firearm, cartridge, capacity, or action type makes a material difference in the outcome of defensive use of firearms. If such data exists, I’d love someone to point me to it. In lieu of that, we are all making suppositions. There is ample evidence that the .22LR is lethal (e.g. Cascade Mall shootings); There is ample evidence that >55g projectiles penetrate through walls, potentially endangering innocents; There is ample evidence that some .22LR ammo can be unreliable in some semi-automatic actions; There is ample evidence that highly-motivated, high body mass, and(or) drug altered people can endure significant body trauma before the threat is eliminated. It just about understanding what factors you expect to encounter in your given situation and what risks you are willing to take in the process of defending yourself. Sort that out and that will give you the answers.
Let me point you to an interesting study of self-defense outcomes that generally concludes that the weapon, cartridge and capacity of the defensive weapon did not make a major impact on the outcomes studied. This is interesting but again, just one point of data. If you live in a situation in which you want to have the best chances of a successful defense against a group of highly motivated drug cartel members, you will likely have extraneous factors to consider rather than the person that is willing to risk the chances of that being low and being mostly focused on defending against a drunk teen breaking in and stealing alcohol and you live in an apartment or other situation in which penetrating a wall and killing an innocent is a big factor/concern.
Link to study:
https://tacticalprofessor.files.wordpress.com/2014/12/tac-5-year-w-tables.pdf
Other notable data points:
1. **FBI Ammunition Testing**: The FBI conducts extensive ammunition testing to determine the performance of various calibers and ammunition types. They have found that shot placement and penetration depth are more critical than caliber size in determining effectiveness.
2. **The Marshall and Sanow Study**: A study conducted by Evan Marshall and Edwin Sanow, "Handgun Stopping Power," analyzed real-world shooting incidents and correlated them with the caliber of the firearm used. Their study suggested that there was a notable difference in stopping power between various calibers, but the data has been debated and criticized for its methodology.
3. **Guns and Ammo Handgun Stopping Power Study**: This publication has conducted tests and published data on the performance of different handgun calibers and ammunition types. However, its findings are often used as a reference point in the ongoing debate rather than definitive conclusions.