Tim Sunels, the owner of Buffalo Bore, highly recommend 45 ACP +P over 10MM for brown bear primarily due to it's 27% larger surface area, or circumference, which makes a larger wound channel. He stated 45ACP +P hardcast is enough to pass through two shoulders on a brown bear.
Personally, I think it's easier to shoot, which would help with follow up shots.
If you're not going to use hardcast, then I don't know if this would change Tim's opinion on the matter.
Maybe if you are hunting bear with a pistol. Which nobody with a brain does.
Most backwoods hunters and guides carry a bear gun as a defensive weapon. A bear never stops and turns sideways so you can put a couple of rounds thru his shoulder. I never saw a single hunter, hunting guide, or bush pilot carrying a 45 as a bear gun. Always a big bore wheel gun (454 Casull, 45 Colt, 460 Rowland, S&W 500) and more recently a Glock 20 - 10mm.
This is the kind of nonsense people who have never been within 1000 yards of a bear repeat on the interwebs. Unless a zoo counts.
Ballistic tests on this topic indicate there is little difference between the standard pressure and the +P rounds. In 45's, It's about 10%. Given their higher velocity, one would expect more penetration from the +P rounds. Not true.
Federal says +P defensive hollow points are actually less likely to overpenetrate. The faster velocity of the +P rounds makes the round āopen upā quicker inside the target, bringing it to a halt in about the same space as a normal pressure round.
It's true not all hard casts are hollow points. So the solid hardcast +p is likely to penetrate more. That still doesn't guanrantee better or more effective. As with all hunting or defense, it's about shot placement.
When you piss off or surprise a bear who becomes aggressive and you have to draw and fire, you have a few seconds to drop him. Maybe you get two shots off before it shreds you. If you hit something vital he may stop. Rounds often deflect and bounce off a bears skull. Try running backwards under duress and putting a round up a charging bears snout sometime. You can get lucky and he pauses to stand up on his hind legs as part of the "I'm about to kill you" posturing angry bears often do.
Shoot a large bear with any 45 ACP or +P and you better be a nationally ranked marksman or luckiest son of a bitch on the planet.