I own 5 .338WM rifles always loaded in Grizzly country with 250NPs at 2750-2800 fps-mv and I own 3-9.3 rifles loaded with 286 NPs at 2400 fps-mv. I would rate them about equal in this scenario and would be comfortable with either.

I would, however, prefer my custom .375H&H P-64 "shorty" with 300 NPs loaded to 2500 fps-mv and just got a Browning Safari CRF in .458WM to customize as my final Grizzly rifle, probably with 450 SAFs at 2150-2200 fps-mv. I WOULD prefer this over ANY other rifle as I have been close enough to Grizzlies to smell them several times and believe in bigger is best.