A handgun is a more mobile weapon. You can go get the
kids, grab the phone, answer the door more easily with a
handgun. You can also use empty hand tactics, more easily,
against knives etc with a handgun.
The shotgun is a stationary weapon (in general). It would be
the artillery that the badguy would have to get through to get
into your safe room etc. The shotgun can be a mobile
weapon if needed. It should be trained in a CQB position with
mocement to make it more functional. It can also become a
good impact weapon.
In Ca. a SMG is not an option. I really do like the handgun/
shotgun home defense combination in all circunstances. An
SMG could definatley be put in the mix though.
This is a clip from yesterdays shotgun training.