Considering that the US military still teaches room clearing with m16s to recruits, and m4 carbines are used by everybody else in theater backed up with shotguns and short-barreled m249s, I don't think that SMGs would superior to semi-automatic carbines in most room clearing situations.
The only penalties I could think of that would make sense would rounds penetrating the walls into other houses, room and possibly killing hostages, friendlies or non-combatants. This problem is fixed with frangible rounds. https://en.wikipedia.org/wiki/Frangible
As for opening a door, usually the guy opening the door isn't the first one in, because he probably doesn't have both his hands on his weapon, or is off balanced.