I'd go with the 4" 357. S&W, Ruger, Tarus, Rossi, (personally a Python fan,,but daaaum they're expensive just to have laying around for the more inteligent thug who breaks in when your not home to pillage). All are fully reliable, and point and pull isn't too hard to remember even when adrenaline kicks in. The Charter .44 Special Bulldog mentioned is also an excellent choice.
Where do you shotgun guys keep 'em so that they're handy? Gun rack over the bed? Under bed with the dust bunnies? Or,, do you keep them in a much more unhandy location due to their size, bulkiness, uglyness in the homey comfortable look of the bedroom or study? While a shotgun is undeniabley a top choice for self defence (or close range offense, for that matter),are you as likely to actually pick it up and go investigate as you would be to grab a handgun that's far less conspicuous?
As the old Texas Ranger who wore his pistol to an awards banquet said to the matriarch when she asked if the pistol meant he expected trouble,,,"No mam, I'd a brung my rifle if I'd thought there'd be trouble.
Bob