For a novice, even getting two chest shots on a person at 10 yards is not easy with a subcompact/snub-nose. Add in low-light (most defense situations occur at night), adrenaline, etc. There's a reason veteran shooters shy away from those types of guns for concealed carry.
Either way, it is absurd to limit all civilians to puff guns because some people hold delusions about their godly shooting abilities.
And that's the reason why magazine capacity bans only hurt legitimate uses. When and IF you have to use a gun in self defense, you want as many bullets as possible because most of them are going to miss your target no matter how good you are.