Actually, in and of themselves both of these statements are foolish:
1.) You need a cannon of such and such a caliber and so and so muzzle velocity and energy (you actually need the momentum, not the energy, but no one calculates that)
2.) You need maximum proficiency.
Why are they, in and of themselves, foolish? Because like all things Internet, people always go to the extreme of one and exclude the other. You'll have one guy arguing that you need a revolver in .45-70 (ever try shooting one?), and the other that wants to take on grizz with a .22LR because he's soooo accurate with one (ever try to stop anything of any real size with a .22LR?).
When in fact, what you need is a gun that is powerful enough, that you are also proficient with.
In reality, last I checked, there's less than 400 grizz in CONUS. I've camped in those places, and seen plenty of sign (front paw prints the size of dinner plates, rear paws that looked like it was wearing wheel rims as shoes), and NEVER saw a grizz. They'd run a commando raid into our camp at night -- waking NO ONE -- see there's no food and move on. Eerie feeling. But I think that grizz learned to fear man in CONUS, after being hunted to near extinction.
In certain arts of Canada and Alaska, such is not the case. They are above you on the food chain and know it. Talking to people who lived in AK, they all said the same thing, the top three guns were a .338 Win Mag rifle, a 12 gauge stoked with Brenneke hard slugs, or a .45-70 all long guns. If you were stuck with only a handgun, a .44 Mag was considered marginal, a .454 much better. It was a simply fact of life that you learned to shoot them well by shooting them, not pussyfooting with light calibers hoping your proficiency would transfer when the bear stuff hit the fan.
So, if you live there, you darn well better get a big lead thrower and you'd better get proficient with it.
Anywhere else, a .357/10mm will do anything you need, unless you want to hunt bears or moose with a handgun, where a .44 Mag would be a good idea.
Wilderness topics really always boil down to one decision making process:
Determine what is needed where you live, and become proficient with it. Doesn't matter if it's knives, axes, guns, shelter, etc.