Sample size is awfully small (7).
Despite this, I think the case may be strong case that one doesn't need large ammo capacity to deter robbery in public places, given that's what most of these cases are. It seems robbers generally want to go through as little trouble as possible, and a handgun of any sort immediately makes the confrontation no longer worth their while.
However, if someone fears some other kind of encounter, say with people who are drugged or have other intents that would drive them to stick around for any reason after the first shot is fired, then more ammo could be life-saving, especially if you're dealing with more than one determined assailant.