>I always thought that SMGs were the perfect weapon for home defense, actually.
In a team? Yeah. On your own? Doubtful. Same is true for assault rifles, the mags are small because it's assumed your buddy can cover you when you're reloading.
Home invasions take place over a period of minutes and you need to be fighting on a single mag the entire time, which means either a regular semi auto pistol or if it's full auto it needs to have a large magazine and a lot of bullets. Or ridiculous discipline.
That's one reason why the machine gun ban is ridiculous, it can't even be used effectively by people.