On youtube there are a lot of videos showing actual penetration of various calibers. I always shied away from a .357 simple because I was worried about over penetration of the neighbors house.
In one video the 5.56 actually had the least amount of penetration using mock sheetrock walls. It only went through two walls and into the 3rd before the bullet broke up. Even the 12ga with 7shot went through the 3rd wall.
The .45, .357, 12ga 00, and 9mm all went into the 4th wall. They’ve even found where the sheetrock will fill the void in a HP round preventing it from expanding.
I've heard "over-penetration" mentioned time after time, and you know what? In a real-life gunfight, the majority of the shots fired miss the target entirely-- so I consider that "over-penetration" is simply not a valid concern.
My main concern is that my weapon will be effective against an attacker. If I shoot, I will do so because it's a Life and Death situation. I must stop my assailant or I will die, so I want a weapon and ammo that makes big holes and leaves big exit wounds. The possibility that someone downrange may stop a stray bullet is fairly remote, but the chances of losing a fight due to poor penetration is a real possibility.
I'm keeping my .357 loaded with Hydrashoks and my 12-ga with #1 buckshot. Good for a minimum of 12" penetration in ballistic gelatin, effective when used as directed.