I do not have enough resolution using a handgun on a Grizzly to offer an opinion. Other then I would not want to depend upon bear spray alone with the high risk of blinding myself in a breeze.
The best and most clear analogy I can offer in this example of the HP VS the hard cast is this:
Imagine a small whitetail deer being hit through the chest/lungs with a 375HH using a monolithic solid non-expanding bullet. At say 100 yards, what will be the reaction of the deer? This is with a 300 grain bullet doing 2600fps, and providing about 4400 ft lbs of energy.
The deer will run off and die 75-100 yards away.
Now shoot the same deer with a .270 Winchester. This is a 130 grain soft point bullet at 3000 fps providing just a bit more then half the Ft Lb of Energy at 2500.
The result? The deer will likely fall where it stands, or run a few feet/yards and be dead. How? The 375HH is far more powerful then the puny little 270! Nearly twice the muzzle energy to boot! Pay attention to bullet construction for the size of the animal. I don't golf, but I'm guessing those golfers carry a selection of clubs for a reason. There is not one that works best in all situations. Just because that big wooden one can whack the ball far does not mean it's the proper choice near the hole!
Years ago the folks racing to cast and shoot monster lead from the .44 was to see what thick skinned game could be taken. This theory left people feeling that a Randy Garrett 310gr sledgehammer hard cast .44 mag load could kill buffalo and elephant so it must be the most powerful load possible. If it penetrated a Bison, it should blow through a simple black bear with power to spare. This is all true!
Just shooting that hole through the chest absolutely kills the bear, but the time it takes is on average longer and with less visual impact and disruption of the "moment" It's like shooting a field point arrow through and animal rather then a broad head.
In the 12 years I was wildlife manager, we killed and relocated a lot of bears. One of my associates Ralph Flowers killed over 2000 black bears, he had about 10 years head start on me as a damage control manager. This series of opinions has very high resolution to base these statements on. I'm not taking about seeing a few dozen bears shot. Confronting a bear that has been snared is filled with adrenaline and all sorts of high performance additives. Flattening this bear when he charges full speed at you and has the snare stop him only to have him spring up and try again is very good at ramping up your pulse.
This is a much different animal to kill then a bear at tree line eating berries. I have shot quite a few of the Garrett loads at these bears. In cases without a CNS hit, or a structural skeleton hit they had nearly zero indication of bullet impact. Quite a few times, I wondered if I had missed completely. When using a 240 grain XTP at 1400fps, the results were completely different and much more decisive.
I'm not suggesting anyone believe this if they feel otherwise. By all means use what you like. I'm only sharing what I learned first hand in person. None of this was read in a magazine and retyped here. All this is from my personal on site with my personal experience doing this.