Hi jaxenro, discounting rifle shootings, all one needs to do is put a bullet into an organ or totally through a body to have the largest benefit. Rifle wounds stop by shock, most handgun wounds by bleed out. Any more handgun power than necessary is wasted energy. The bigger the hole the better. Our 1850's BP revolvers have enough energy to take four or more people down if they are standing behind one another.
IMO we don't see significant improvement in handguns because the science is settled, there's little more to discover. Of course small improvements are made with time, but it's like polishing a turd.
However, there's always an effort on how to kill someone faster and better. Too bad.
Regards,
Richard