I can assure you that if you asked enough retired cops who are now dealers about any caliber aside from their favorite, you will be told it isn't an effective manstopper or too much gun and will get you thrown in prison for premeditated murder.
I've never heard of someone suggesting that a certain caliber constituted premeditated murder, or in other words first degree homicide. Perhaps that was an exaggeration.
I've been around both working and retired officers, and "favorite" among LE tend to be from the gun they found most accurate or were first trained to use. So some like .38/.357, some 9mm, some .40 S&W, and some .45 acp. You will find a few that love .41 mag, and .44 special. (I am very tired of the "European" argument..., "Hey .32 ACP worked for years for European police". Sorry, the mind-set where the .32 acp was used, is skewed to something other than dropping an armed assailant first, and all else secondary. In those countries where the .32 acp was the norm for police, the "political" concern was about how much damage the police might do to the poor criminal (first), and then protection of the officer. Not the other way round.)
ANY of the rounds I mentioned will do the job with reasonable shot placement, as opposed to "perfect" shot placement, which is something else that cause LE officers to prefer certain calibers. Some, OK more than half, are mediocre shots. Perfect placement will work for any round and a .22 LR is then a "man-stopper". REMEMBER too that LE Officers will also judge a round based on their confidence in being able to go toward a suspect, confront, and engage (that's what police do) while most civilians have the option (in some states the "duty") to retreat, and only need a round to halt a fight, and cause a suspect to flee, for it to be "effective".
It also depends on where you may need to use the handgun for SD. One school of thought is that you using a lighter caliber handgun inside a home even if not immediately effective on impact, will encourage the assailant to retreat and flee. Outside the home, some consider it a good round to injure an attacker to allow you to escape. Some think it's a great round, in that it hits hard for its size, and its size allows you to carry it in hot weather and light clothing, so you DO have a gun when the fight occurs.
I am LE, and I think the .380 acp round is lighter than what I would call a minimum, with a 9mm HP or a .38 +P HP as the smallest that I would go, but again, I have had 20 years of training plus 4.5 years active military service, and my viewpoint is skewed from that. I know of an older lady who has a Colt 6-shot, .32 Long, snub-nosed, detective special her late police-detective husband left her..., and at 70 years of age, she can hit a 4" disc at 25 feet. I don't doubt that she would win an encounter vs a badguy in her home. .32 long is NOT my choice for SD but the first part of the equation is can YOU shoot it well, and hit what you need to hit when under stress? Get what you can shoot well, then practice practice practice.
OH btw .38 is cheaper than .380. I just got a 7 shot 2" Taurus, for an extra gun around the house. You want small try SP 101.
LD