Tim over at Gun Nuts Media has a great piece on why capacity matters.
Read the whole thing. It has gems like:
We do not know what it will take to actually stop a violent attacker. People often make the mistake of believing that somehow a gunfight or a shooting is going to happen on their terms. Think logically about that for a second: We?re talking about a situation which has spun so far out of control that your last option to resolve it without ending up in a wheelchair or a body bag is to aim a firearm at another human being and shoot them.
We?ve discussed expressing capacity as time, but here it?s important that we also see capacity as opportunity. More opportunity to make a tough shot against a hostile moving and using cover. More opportunity to get a fight-stopping round on target, ending the bad guy?s hostile actions. More opportunity to win. When the bullets are going both ways, more opportunities to fire at the threat is always superior to fewer ones.
(Emphasis in original, but in italics. Changed here to bold for clarity since WordPress’ “blockquote” feature italicize all the quoted text.)