I'm just learning about shotguns, too....
But I would never suggest that a person (like this one) get a dog for protection. I'd suggest that almost any gun combined with a marginally trained person is safer than a protection dog.
Dogs are alive and active in / around the house all day (not tucked under your mattress or in a safe). If the mailman, UPS, meter reader or the neighbor's kid arrives, would you trust that your doberman will decipher friend from foe?
With dogs, there is always the "oh I forget to put him in the pen.." moment at just the wrong time.
Guns, of any type, stay put.... and don't do anything until you do.