Like many, I prefer the largest caliber I can have if I were to need it....but I am a small man and concealing a large pistol is not practical all the time. Do I think a 22 will stop a raging attack? Very unlikely unless one were to get very lucky. But if the option is that or nothing, I'll carry the mini.
I travel in my work, often to places with a "no weapons" policy. I have to have something that will go un noticed in a visual inspection of my vehicle. Otherwise, I would have to carry nothing at all.
Not all situations are perfect, nor the solution. No, a man cannot shoot the bullseye out with a derringer. But in a close combat situation, if I can place it to your cranial cavity, I've increased my odds a bit.....JMO.
Ben