Personally, it has been proven a bear spray canister is more effective. I myslf have a concealled carry firearm permit. I would be comfy in black bear country with my .45 acp . Grizzly is another story. Bear spray first! Rifle wise if I was carrying in grizz country. I would take a AR 15 chambered in 6.8 REM or 6.5 Grendal. Or a AR 10 in .308 , 450 Bushmaster, or 458 socom. My preference would be bear spray.
I just finished reading Andrew Skurka, The Ultimate Hikers Gear List. He was Charged three times bye Grizzlies in the yukon. One time he threw his hiking pole at the Bear before reaching for Pepper Spray! He said Bear ran away so fast it Pooped Berries for 20 feet!
My opinion is it wasnt his time to die! Or he is a very good story teller!
A Charging Grizzley is a Massive animal, that requires Large caliber Firearms with excellent shot placement to save your butt! 25 or thirty round magazines ,I would suggest as well.
I have to beleive odds are better with Bear Spray?
I hope I never find out if Im right! I am very happy with a educated guess! Good Luck, Happy trails