The stretch cavity from a 357 would blow a squirrel apart. A human has enough mass to absorb the energy. Look, imagine it this way. You shoot a 2'' cube of ballistic gel with a 357 and it blows it into little pieces strewn about the countryside. Now take that same 357 and shoot a 12'' cube of gel. The 12'' block will have enough mass to contain the stretch cavity, which will then collapse back in on itself, leaving you with a nice pencil sized hole drilled through the entire block. Now shoot another 12'' square block with a .38 Special. You'll see a smaller stretch cavity on high speed video, BUT...the resulting permanent wound track will be indistinguishable from the 357: a nice, pencil-sized hole drilled through the entire block. So what's the advantage of the 357 over the 38? Imagine that you have both in a modern, barrier blind hollow point. Let's say both bullets get 18'' in gel because the 357 bullet is made to expand more aggressively, thereby limiting its penetration, whereas the 38 expands less aggressively, allowing it to penetrate further. Now shoot both rounds through a car door. The 357, even though it technically penetrates the same distance through bare gel as the 38, will stand a much better chance of making it through the door, and with enough energy to do damage on the other side. If all bad guys ran around shirtless and never used cover then .32 ACP would be adequate for just about all but the biggest, most muscular humans. Or certainly .380 would be. The reason for duty caliber and magnum cartridges is because bad guys wear clothes and typically try to get behind stuff when you shoot at them. Let's say you have a big bad guy wearing a leather jacket hiding behind a car door with the window rolled down. A .380 probably isn't going to get the job done. A 9mm might. A 10mm is a safer bet. Well, hope that's clear as mud. All these bullets are going to leave very similar permanent wound tracks in real human flesh, with similar amounts of trauma, blood loss, and resulting drop in blood pressure. But the bigger, more powerful rounds stand a better chance of making it to the vitals in all circumstances.