In similar barrel lengths the 25 is way ahead of the
22 LR penetration and the 22 short is not even in the running. Not to
start any disputes but I find stories about 25 FMJ bullets getting
stuck in pectoral muscles with no further penetration impossible to
believe. Jell tests show 25 FMJ penetration of 12"-13" and 32 FMJ
penetration of around 16"-18". In my own limited tests in wood good
32 FMJ ammo will slightly outpenetrate good 380 FMJ. As with any
handgun round shot placement is crucial but carrying a 25 with good
FMJ ammo is a long way from being unarmed.
This is why I have greater faith in the .32 ACP than the .380. The bullets are generally running out the barrel at the same velocities and the smaller FMJ slugs tend to penetrate more deeply than the larger, heavier slugs (9mm Luger/.45 ACP FMJ ammunition analogy.)
While the .25 ACP is slightly heavier and wider than the .22 LR, the FMJ configuration of the .25 lends itself to deeper penetration. Such is the genius of John Moses Browning.
Scott