I agree wth the sentiment about not bringing a pistol to a gunsfight- a pistol is only for use when a longgun is not convenient or practicala nd I can't see where in a house a shotgun,carbine, or rifle is inconvenient.

An armed intruder is likely to be armed with a pistol- its easy for him to carry, and its not an encumbrance as he''s carrying your valuables out. Why would you fight on the same level and use a handgun when a shotgun is far superior?

As far as penetration goes, a handhun 9mm and up is going to penetrate more walls and is more likely to intrude intoyor neghbor's home than a shotgun loaded with birdshot. For that matter, an AR-15 carbine loaded with lightweight hollowpoints or even frangible bullets is going to penetrate less building materials and be a mch better manstoper than any handgun.