Personally I have skipped the 300 Mag class altogether... I don't need that kind of range here in Ontario. I use a 308 because it's light recoiling, powerful enough and inexpensive to feed (and I can always find ammo, though the 300 Win Mag is pretty common too). If I know there would be a chance i would be hunting grizzly or even encountering one I would probably take a medium bore rifle like my 375 H&H. I would feel pretty comfortable with a 338 Win Mag as well... For me, who likes to own several rifles at a time I find the 300 to be a compromise cartridge that is too much for 99% of what I do and not enough for the rest. It'll kill anything you hit properly but the medium bore just gives that much more of a whack...
Jeff