Once, ONCE, I had to "clear" my house. I called my wife on my way home from a late night meeting. One of the dogs was barking at a small door leading to an attic crawl space off our bedroom. She was in the office with the dogs, a S&W 686, a telephone, and a large easy chair in front of the closed door.
I had my choice of weapons, including a 20-gauge pump. I chose a .45 Goverment and a SureFire 9P flashlight. I figured I could hold the gun close in by my side as I peeked under beds, behind doors, in showers and tubs, around corners, in closets, under the stairs. The light might temporarily stun someone hiding in a dark space waiting to jump out. By the time I finished up in the basement the grips were WET from my nervous sweat. That 5-10 minutes of "house clearing" sucked, but I didn't feel undergunned with the pistol. I believe I would have felt awkward and less mobile doing all that with a shotgun.
Have I "investigated" downstairs noises before? Yeah, like the time the wind blew in the kitchen window and knocked something off the dish drying rack. But I stood silently at the bedroom door for several minutes, listening intently, gathering my wits, and letting my eyes become accustomed to the darkness. Then I sent the two dogs (brothers) downstairs first, about 15 seconds ahead of me. They didn't alert on anything, and they know where to look, because I play hide-and-seek with them.
But if I ever heard a DEFINITIVE smash/entry, with voices and heavy bootsteps, it's a) call police on bedroom cell phone and leave line open b)wife in the closet with revolver c) soft body armor on d)rack shotgun and point at locked bedroom door. And my dogs better not get in the way.