My point being you're using an LE standard, not a SD standard. If you want a .380 to go 12" use a fmj. FMJ is a poor choice for SD though, so premium HP's. In any SD round, any caliber, premium HP. Period IMO. Even though the .45 ball has a substantial following for SD and for most of the successful SD shootings through history premium HP's didn't exist.
The 9mm for LE even with premiums is completely inadequate IMO, and lots of cops opinions. BUT lots of other cops say it's good enough. Last I checked in LE uses it has among the poorest reputation compared to the other common LE calibers, .40 10mm and 45 rounding out the top 4. So imo, for duty use, it's junk, garbage and useless
But for SD I consider it acceptable. Different standards. On duty I may need to punch through a bad guys shoulder, heavy clothes and reach the vitals. Odds are I'm dealing with someone who has a strong motivation to not go down and to try and kill me instead. It's a fairly high need.
For SD I need it to travel 4" into soft tissue. Because 99.9999999%(making up numbers here) of SD shootings will leave muzzle burns and site imprints on the target, they're that close and the heart is about 1.5 inches deep. That 1.5" is probably (playing statistics here) needed on a bad guy who is looking for an easy score and if popped with blanks will likely run like hell because he's looking for a victim and not a fight. Of course you may be face to face with a motivated bad guy but odds are slim. And even if you're dealing with a motivated bad guy odds are he's close, odds are he's facing you, and odds are he'll go down with a well placed shot.
For that 1.5 inches needed the 380 will do the job, the 9mm will do it a bit better (same expanded bullet size with a little more oomph and a little more mass) the .40 will do it even better, the 10 mm will do it even better (same thing here as the 380/9mm comparison) and the .45 *may* so it even better. If all we look at it which one does the most and trash anything that isn't what we consider best we're doing an un-needed disservice to all the tools that will do the job. If a .380 kills the bad guy, the 45 isn't going to kill them any deader. If .380 is the biggest bang a shooter can handle, it's the perfect tool for them.
So what else has been used at SD ranges? .22lr and mag. Which are bunny rounds imo. .25acp has just enough energy to travel 10 feet before it tumbles and yet it was used. In basic I'm sure you got to watch the video of the cop taking a .25 in the ribs and dieing for 4 minutes. I hate that video. But the lowly .25 was used. Most rimfires have been used but they're completely inadequate for all uses imo. They're potentially deadly firecrackers. Moving up to what is the minimum imo is the .380. It's usefulness beyond target shooting is SD. It goes no further, can't be used as a duty round, hunting round anything. It's the minimum. Anything bigger is better but you shouldn't look any lower for its intended purpose and it will do the job needed. If your purpose is higher, it's an automatic no.
There is no 'best' in firearms, there is only acceptable and unacceptable.