The .455 is a powder puff and the .45 ACP more or less as well.

Having said that either would be better than nothing.

Years ago I was involved in a fight with a rather small black bear. I emptied a .44 Magnum into it. Each of the shots were lethal but had little noticeable immediate effect on the bear except the first at which it dropped and lay still until dogs pounced on it, when it exploded.

Bear was at my ankles and my then-14-year-old son dove over my shoulder and more or less "bayoneted" it with one round of 7x57R.

Lots of black bear have been killed with handguns and this one would no doubt have succumbed to the first shot had it been left to stiffen up. But the pack of dogs pounced on it and that commenced the rather short but very exciting fight.

I found later that all the Nosler 240 JHP bullets had acted like FMJ's & just poked holes. I recovered one and compared it to one I later tested in my media and it was identical. That was a case where an expanding bullet likely would have finished the fight quicker, maybe a lot quicker, saved some wounds on dogs and a few extra heartbeats on the rest of us, too.