A good answer to your question needs more specifics, but in general, suppressed handguns with home-defense or target ammo are still loud enough to gain attention.

On the other hand, subsonic ammo will be pretty quiet and reduce the noise drastically, but unless you have the semi-auto mechanics tuned properly, the gun won't cycle the next round in very well. I can't speak to the stopping power of subsonic ammo but again, it probably requires specifics to give an accurate answer.