What length barrel are you citing?
I got 1900-2100 FPS out of a 16” barrel with 300 gr. bullets.
Having spoken to people who have actually used .50AE on bears, it works very well, much better than .44 mag. and miles ahead of .45 acp!
The Auto-mag V is reasonably light, unlike the Desert Eagle, recoil is still reasonable.
I’ve fired 500SW, do not want one, too punishing to the shooter.
I prefer a pistol as a rifle/shotgun can be awkward.
I was using a 6” barrel; finding a long-barreled 50 AE is nearly impossible. However, .45-70 is readily available in longer barrels - it’s a rifle cartridge, not a pistol cartridge. And you can find .45-70 ammo all over - is 50 AE easy to find?
I worked half a dozen summers as a guide in Alaska (outside of Dillingham, up in the 5 lakes area), and about the only thing any serious guide would consider is either a .45-70 or a 12GA with slugs. Most .45-70s were Marlin 1895s with a barrel cut down to 18” (just a little longer than the magazine). Also make a handy club if needed!
A few liked 458s and 30-06s and some used 338s (mainly way up North in polar bear country, where longer shots might be needed), but it was shoulder-fired weapons to a man, and usually levers or pumps (nice and reliable and easy to operate, even with a bum arm). Semi-autos were never seen - not enough trust they’d always go bang multiple times, and it’s hard to clean the action if it falls in sand, dirt, or - as I’ve seen once - filled with ice.
Some guys carried pistols as well (I carried a Glock G20 - capable for anything smaller than a bear or large buck), but those were backup or for smaller predators. For the grizzlies - or even scarier, bull moose in mating season - it was the .45-70 that protected you.
For grizzlies, the general consensus was too big is almost big enough - you just don’t want to risk anything smaller or less accurate. You get maybe 2-3 shots off on a charging grizzly before they’re on you - every shot MUST count, and the must have enough punch to go through the front of the bear deep into the heart and CNS area.
Personally, I’ll take the .45-70 every time - it’s proven in the field for grizzly and even polar bear work. If you’re comfortable with the 50AE, go for it, but I never saw it out in the field, and have a hard time believing any pistol cartridge will provide equivalent energy to a strong rifle cartridge, and I personally prefer the stability and accuracy I get with a rifle as compared to a pistol - especially a strong recoiling pistol.