None of the game you mentioned you would like to hunt requires a Magnum caliber rifle, but both rifles you mentioned will surely get the job done. I like the .30-06 and will reccomend that rifle above the .300 Win Mag, especially if you are new to shooting centerfire rifles. I think that if you handload the .30-06 is more versitile than the .300 Win, but that is just my opinion. I don't really think that Magnum cartridges were really invented to improve long range hunting but to hit harder within normal hunting ranges so that most animals in heavy cover didn't need to be tracked. Check out http://www.federalpremium.com/default.asp?br=1
use their ballistics catalog to help you to decide if you need the Magnum rifle or not.