Round placement is as important, if not more so, than caliber or round energy/grain wt.
Your specific and/or situational applications should be the second factor in caliber choice as a .40 cal will perform better at 60 meters than a .45 - though a .45 will transfer more energy/knockdown at 10 meters. In a true CQB tactical application I prefer a .45 cal on a 1911 frame (Kimber) or a Sig P220. For general all purpose type CCW I prefer a Sig P239 in .40cal - reliable, safe and lightweight.
In any application Cor-Bon manufactures what I believe to be the best one-shot-stop mass-produced ammo. You may find hand loads in +P or +P+ that might perform slightly better but then open yourself to an overzealous DA or plaintiff’s attorneys should you have to experience the unfortunate event of terminating a life-threatening situation. Never thought much of the 9mm due to over penetration thus the need for sub-sonic rounds in non-suppressed tactics. I know of few Agency operators who carry a 9mm.
First master weapon safety. Then learn the levels of force escalation, then terminal round placement, then multiples, i.e. double tap and two rounds to the center mass one to the head.
Always try everything to extract yourself from a bad situation - if you cannot then go loud.
