I've heard of the same theory. Can't recall where I came across it, it was some years ago. I suspect there may be something to it. I mean, one of the objects, whether with
handgun or rifle, is to have the bullet expend all or most of its' energy IN the target.
While it's in the target it's dumping energy so, even if it passes thru/exits, the longer it takes to do so the more energy is dumped in the target.
Looking at shooting reports, stopping power reports/calculations, etc. it's hard to dismiss the old, heavy, relatively slow moving slugs such as 44Spec., 45Colt, and the 45ACP.
They don't rely on expansion like the smaller, higher velocity slugs from the 9mm, or
357mag. That said however, the newer ammo for the smaller calibers seems to be pretty reliable for expansion - something that wasn't always the case years ago.
I've got a 9mm, and a 357mag., but my favorite is the 45Colt. Pleasant to shoot, and I feel comfortable relying on that big slug to do the job.
Heck, look at the Moros in the Phillipines. The Army went to the 38, and their troops were getting hacked up by those guys with the machetes. A switch back to 45Colt guns put a stop to that sort of thing.
I've said it before, but would you rather be hit with a baseball going 90mph, or a bowling ball doing 50mph.? That baseball is gonna' hurt for sure, but the big one's gonna' knock ya' on your caboose!