@orionengnr: I am not sure I completely follow your response, but, what I think I hear you saying is, there is more to think about than capacity. If so, I'd agree with that, and don't think that is necessarily at odds.
The math of the OP is telling me - if all else is equal, more capacity gives you a greater likelihood of making the stop. I think that's pretty hard to argue with.
You though, seem to be saying that, all else may not be equal, i.e. you might have a hit probability of 0.25 with gun A and 0.50 with gun B that you are very familiar and confident with, that has excellent sights/practical accuracy. Then even if gun B has fewer shots, it might still be your best bet. That can also be true.
So here's two other calculations (1 assailant):
1. Hit probability per shot = 0.25, 10 shot capacity, probability of two or more hits when empty, is 0.76
2. Hit probability per shot = 0.50, 5 shot capacity, probability of two or more hits when empty, is 0.81
So yes, *if* you shoot much better with one gun than another, that can outweigh a capacity disadvantage.
See free online binomial distribution calculator at: