Dead is dead.
You can get into arguments on bang flops vs running off.
We could debate that they all die at the same speed vs how fast or far they bleed vs how scared or suprised they are.
It can go on forever. One can easily argue that supersonic does more damage because it probably frags more. More damage is bled out quicker.
OTOH I shot one the other day with a slow but not subsonic bullet. Deer lived about as long as the ones I've shot with 308s and 300s time wise. But he wasnt' nearly spooked, and only decided to make a last run because he was getting wobbly. You could argue though, had it been a loud blast he'd have run the whole time.. bleeding quicker due to elevated heart rate and BP.
Bottom line here, I"ve shot not 100 deer subsonic, but probably about 15 or so. And not with a can or fancy stuff. but with a 45 acp and 44 special. They run off and die like almost every other deer I've shot with supersonic.
There is no magic when you break the sound barrier. After all that can be just 1 fps faster than sub....
I will agree though, that seemingly the faster the bullet goes, and the more frangible it is, when shot not into a CNS spot or major bones. IE ribs hitting both lungs, the faster it goes the more the odds are of bang flops.
Being a bowhunter for many years with over 100 bowkills(all subsonic, grins), I expect the deer to run when I shoot unless I'm head shooting(rifle). You go find em no big deal. If you need a bang flop, then CNS is where I shoot or I don't shoot at all.
Where we are talking here is a difference between supersonic and sub with an AAC vs something like the x39 round, there will never be enough difference to me, to make it worth worrying about. The difference to be seen will be the subsonic vs a 257 wtby or such. Even then, my buddy has yet to see a bang flop with the 257, but none have gone more than about 30-50 yards ever.
The only reason to use subsonic is a noise issue. If thats your case, then pick the right setup and projectile, know your limits and stay within those bounds and then know that inside those bounds those deer/pigs will be as dead as any supersonic round ever will be average wise.
The only deer I've seen survive a centerfire rifle shot was a double lunged buck shot with 06 and 165 SGKs at about 125 yards.... thats definitely supersonic.
If I had a choice though and noise was not an issue, then why limit myself to a round that can't perform at the distances I can. So when noise is not an issue, I'm rarely carrying anything thats not effective in the wind, out to around 600 plus yards or so. Unless I"m feeling froggy and decide to take the 1911, or the slow levers, or my MZs and such.
