I've always found these discussions strange. In my early days, the only really different then normal stopping handguns were 45 Colt, with heavy loads, and 44 magnum.
One common thread is that 260 grain 44 or 45 Colt bullets, with thin jacketed hollow points, or soft lead, at anywhere from 900-1200 fps, or faster, seem to work VERY well, and, have done so for nearly 150 years.
Oddly enough, this seems lost on the handgun community.
The 45 ACP has worked fairly well, but, I think it's stopping power could be increased considerably by 260 grain bullets, and, 45 Detonics allows these to move in the 1000 fps range, out of a semi-auto pistol.
I've also had great comments from Detonics with 200 grain bullets at 1200 fps, in 45 Detonics.
I believe that due to the 'over-penetration' boogie man, a threat created by the FBI and many LEO agencies to validate moving to high capacity semiauto pistols, the rest of the industry has taken a large drink from the same cup.
That said, the laws of physics seem to apply, at least in trying to slow down a heavier moving object, and, the result aid the ability to incapacitate. TO make it very simple, the higher the bullet weight, the harder it is to slow the bullet down, and, when a large caliber, heavy bullet opens up like a parachute, and, thanks to it's heavy weight, creates a large, deep hole THROUGH the target, rather then stopping 12-15" in, it tends to inhibit the targets ability to continue.
We do have some handgun rounds now that are seriously in another category as far as stopping power. The 460 S&@, with a 200 grain 45 caliber bullet, at 2300 fps is a handgun with rifle statistics. I see no reason that a 475 Linebaugh, .500 S&@, .500 Maximum, etc. that all come into the 3000ft-lbs of energy range, 6 times that of the average service caliber, aren't considered REAL stopping rounds, and guns. Yes Martha, you can tune some of these guns and calibers into deer, SD rounds, with 200-265 grain fast expanding, thin jacketed bullets, and, yes, they will work 4-6 times better then ANY of the service rounds.
The real stopping rounds read:
30-06, .308, 7.62 x 54R, 8mm, and up. Also, a very strong case can be made for the 7.62 x 39 as being an effective SD round...
Finally, long for caliber bullets have an advantage: they wobble, and, geometrically increase the wound channel due to instability.
You want my worst nightmare? Getting shot by a 733 grain, cup point .510" caliber bullet, out of a gun incapable of stabilizing the bullet, at near point blank range. The thought of an over an inch long, BMG bullet tumbling through my body, at nearly 1200 fps, is truly my worst nightmare. My gunsmith has shot a LOT of deer, buffalo, etc. with heavy caliber handguns, and, he assures me for not quantifiable reason that there is something about getting hit with a .510" 525 grain bullet at 1350 fps that tends to totally get the attention of deer to car sized animals...
Bullet instability, and the chaos that comes with a tumbling, or unstable bullet, read british .303, they didn't make those bullet with wood cores to be nice to the Germans, is an often neglected part of the 'stopping power equation'/.