I disagree with your “not a serious ... “ comment. In most of the infrequent events wherein one has to actually draw a weapon, the choice of caliber is of no importance. A perp holding anything other than his own gun will find that leaving the scene is far more interesting than waiting around to see how big a hole your weapon will make in him.
Most self defense scenarios are resolved in seconds. Having your weapon available rather than having it in your lock-box at home is far more relevant than the size of the bullet.
Been there ... done that. No shots fired but it was interesting to see how fast a guy can run with his pants down around the hips.
That’s why I have an extended mag 12 gauge in the bedroom.
8 shots of OO buck should do the trick.If I have to leave the house to investigate a possible problem,I have an M16A1 or suppressed MP5 to take with me.
But to me a 9mm is pretty far down the food chain,so to speak.The subgun is a little different since 6-8 torso hits is enough.