So, you'd rather be shot at 20ft by a load of #5 shot than a load of buckshot. Dead is dead, then again you might believe that a .300 Win mag is required to kill a whitetail where as a .243 will do all I need it to.
As far as advice, one could also say that your advice is bad as the projectiles you want to throw around inside of a dwelling pose more of a danger to others within the house who may be on the other side of that partition. Or be more apt to breech an exterior wall/window and present a danger to your neighbors if they were to live in close proximity.
As to self defense against humans, answer this, are more people killed in a year by .22lr or the .50 BMG? Are more people electricuted by 110 or 220? Human life is frail and just like everything else shot placement is key. You do it your way, I'll do it mine. Chances are the bad guy would end up the same way but collateral damage and injury to others won't be as prevelant on my end.