in a bad situation, a .22 is better than nothing, its not about size, its about having a weapon when the SHTF. I stopped a guy that meant me bodily harm in his tracks simply by racking a round into the chamber of a .22 LR walther knock off I used to have. so I considered it plenty of stopping power for the situation.
I would go with the Critical Defense rounds.
There is no such thing as Overkill, Dead is Dead!