Random attacks by 5 or more, rare unless one is in a very bad part of town.
Random robberies by groups of 3, rare, but not so rare that one doesn't read about them at least once a week.
Defensive shootings where more than three rounds are absorbed by a bad guy who keeps on attacking, rare, but also not unheard of.
In most cases, just having a gun is good enough.
In some cases, having the gun and actually being willing to use it is good enough.
Other cases, having the gun, being willing to use it, and using it skillfully is good enough.
But in some cases, more is better.
It's hard to think of a case where fewer is actually better, with the exceptions of: 1) the gun with "more" is too big, so doesn't get carried; or 2) for whatever reason, the gun with "fewer" is the only gun the user can shoot all that well.