Welcome to DC!OP....something is better than nothing.
The .380 or 9mm Browning short is OK, but lesser so than the more potent 9mm. . The .25 is a toy, .22 Stinger is better than a .25, just forget all these puny calibers unless it is a last resort. If you do find your life resting on a .25 or .22, they do the best job when placed in an eye or an ear.
If you want great penetration it requires a full metal jacket with low expansion of the bullet. This may cause problems with the bullet exiting the body cleaning doing less damage to the assailant, offering less stopping power and hitting innocent bystanders...
Here are a few penetration tests of stacked newsprint to give you an idea how various ammo performs...
You've obviously done a good bit of web-surfing, but have picked up a lot of Internet Folklore along the way.
If you believe that a .25 ACP is a toy, you really shouldn't be handling firearms at all. If you believe a .22 Stinger is superior to a .25 ACP, you've probably been looking at data comparing a Stinger out of a rifle, with a .25 ACP out of a 2" pistol. From comparable barrel lengths, the .25 has a lower muzzle velocity, but with a much heavier bullet, considerably higher momentum and ME. Both the bullet diameter and sectional density exceed the stinger, and the .25 will outpenetrate the .22 by a wide margin, not to mention the superior reliability of the centerfire round. I would not choose a .22 or a .25 over a larger caliber, but if those were my only options, it would be the .25 hands down.
No doubt, there's a trade-off between penetration & expansion, but since the thread is about .380 ACP, consider the 90 gr. XTP. In denim/calibrated gel tests, it reliably penetrates ~14 inches with perfect expansion, even out of a short-barrelled pocket pistol. This meets the FBI protocol for a service round, and if you want an effective bullet but are concerned about overpenetration, it's about as good as it gets. Be more concerned about collateral damage from the rounds that miss, rather than those that might overpenetrate the intended target.If you want great penetration it requires a full metal jacket with low expansion of the bullet.
Newspaper, particular if it's dry, is almost worthless for assessing the effectiveness of a bullet. No modern JHP will expand much, if at all, in dry paper, so you're basically just comparing FMJ's no matter what bullet you use. Ballistic gel is not perfect, either, but it at least provides a standard for comparison.
Welcome aboard. You can learn a lot on DC.