Being able to make accurate and effective hits on their attackers.
But, of course, this is true no matter how many bullets you have on board. Just because you have a high-capacity pistol doesn't mean that you necessarily have to expend bullets without achieving good target acquisition. I think it's an over-used mythology that people armed with high-capacity weapons are predisposed to spray the landscape wantonly with lead. "Accurate and effective hits on attackers" can be done just as effectively with a Glock as it can be with a Chiefs Special. It all comes down to training, practice and good judgement-and it's up to each individual person to acquire these attributes and to make their own decisions as to which handgun best fits their own unique circumstances and skill level.