I'm no expert, but I read an article about this subject some years ago..

The author maintained that the best choice for "across the bedroom or livingroom" ranges was low base 8s or 9s.... Buckshot blasts through drywall like ahot knife through butter and heavier birdshot like 2s or 4s still tends to penetrate walls fairly well, where the small shot like 8s or 9s doesn't... AND the small shot still creates an awesome wound...A center shot with a skeet load of #9 shot at five yards will drop the most determined perpetrator and create a terrible wound... Odds are you'll need a coroner rather than an ambulance to take the creep away...