Both are do-all Lower 48 states cartridges and will work fine for most of Canadian and Alaskan hunting, If you leave out grizzly and brown bear which are the same species. Both have a plethora of bullets available for reloaders and factory ammo is available everywhere, if you stick to the winchester and remington " regular" magnums. The 7mm Mag recoils less, sharper kick. The .300 Mag recoils more, fast push. Both good cartridges and have killed everything in Norht America and a lot in Africa and elsewhere.