This has to be the most over-analyzed question I run across, and I know because I over-analyzed it myself for quite a while. Online ballistic testing tends to produce contradictory results. As best I understand it, the magic behind a "short barrel hollow point" is simply that it's able to fully expand at lower velocities than would be achieved by a longer barrel.
Some options that seem to perform very well out of short barreled pistols include:
- HST 124, 147 and 150 (micro)
- Winchester Defend 147
- Sig's own "365" hollow point ammo
- Hornady Critical Defense 115 (although it seems to have shallower penetration in the reviews I've read, like 12-13" in gel vs. 16" for the others...however it's also been shown to perform very consistently through a lot of different barriers whereas other HP designs can get clogged and not fully expand)
Out of the above, I'd recommend the HST for two reasons: (1) it's never going to fail and it's a demonstrated performer, and (2) you can order it in 50 round boxes at a reasonable price and run it through your gun without feeling like you're wasting money. Most HP ammo is badly overpriced.
That said, I carry Winchester 147 because I bought a couple boxes of it before I discovered that HST costs less. Eventually I'll shoot off my carry ammo and maybe I'll switch to HST. Maybe not. I really don't worry about it anymore.
But overall it really doesn't matter. If you chose one of the ones I just listed, or one that others here have listed, so long as it runs reliably through your P365, just go with it. They'll all poke holes in things and will offer good terminal performance.