Hallo Guys,

-Shooting the heaviest North American game,-
which will bring down game the FASTEST,-
given EQUALLY HIGH quality bullets of course,:
The.458 Win. Mag., or a hot .338 (-say a .338 RUM or other "Hot" .338) ?!

Chr.

Hit them in the right spot, it will not matter much. I would take the rifle you might shoot best with a good projectile.
I am sure the big bear people would prefer the 458 up close and personal.
The 338 perhaps for extended ranges.

You don't need a 458 for the job and it depends on the critters you want to hunt but the 338 win mag will do it all with energy left over, IMO if you are thinking of the 338 RUM you might just go up in caliber. Actually I'd choose a 30 06 with 180-200 grain bullets over both of them.

< 250yds = 458 WIN

> 250yds = 338 RUM

I'm with mwm464, distance of the game would determine the choice.