Hey Paraguy, this is a great thread, with a wealth of knowledge from many. Consider all options regarding a 12g with a pistol grip only.
There have been previous posts with shoulder/pistol grip options but it really comes down to you and what your comfortable with.
The Personal Defense Annual Issue, has great current articles by Janich, and others, regarding line of fire, in your home, hallways, bookshelves, fireplaces, stairways, neighbors, that is a great read.
The shotgun is about as good as it gets for home defense, but consider your home and domicile. Usually #2, OOBuck, is more than adequate, but consider, with close neighbors, adjoining bedrooms, #4, or #6, or 8 shot.
As others have posted, at SD ranges, 7yds or less, it won;t matter to the BG. There are reduced recoil loads 9-14 pellet loads, that would more than disable a BG at 7yds.
Regardless of brand, Mossberg, Stoeger, Remington, whatever,...the shotgun is on the short list for a home defense weapon.
Fellow shooters I know, stagger their rds.(as I do), sometimes called a "spray & wash" approach. followed up by slugs, which would require more accuracy, but it would be Katy Bar The Door if 6-8 rds. won't end a threat, in a home.
Shotgun tactics are well worth reviewing, the current mag referenced above has some great points to ponder.
Take Care.