I think your own skill level and the ammo used will matter more than the platform.
A few years ago, a guide killed a brown bear in Alaska with 7 rounds of 9mm from a compact Smith and Wesson pistol.
He used buffalo bore 147 gr 9mm hardcast I believe. I think it may be +p.
There are also the outdoorsman rounds in 38 special (a 158 gr +p hardcast) , 357 (180 gr hardcast), 45 and most other rounds.
There is even 380 acp hardcast rounds. 100 gr. You have to wonder how much they would really differ from the 9mm used effectively.
If you've ever seen combat then you know how you'll respond in a seconds matter life or death situation (which an attack by a bear would definitely qualify).
Suppose the guide carried a sig p238 loaded with 7 rounds of the 380 100 gr hardcast, would results be the same?
Personally, I vote yes because the guy could handle himself, he knew bears anatomy so he knew where to aim, and both rounds will get significant penetration even through barriers (in this case, fat, muscle, bone).
The point being: training, know how you react. Platform, know what you shoot best and what you're willing to carry (all the time). Today, ammunition exists that can get the job done in most calibers.
Would a 44 magnum have been better? It's the traditional bear medicine. That guide probably wishes, but he got it done and chose the right "arrow".
Loaded up with premium jhp rounds, that story would have a different ending.
Hardcast plus p flat points in numerous calibers can get the job done, so know the anatomy and which type of gun you can fire quickly and accurately.