The .308 and .30-06 have been putting venison in freezers reliably for years. A question though, have you any "other" deer medicine? If, say you already have a .270, you'd gain little by adding a .308 or .30-06 to your battery. On the other hand, how convinced are you you'll "get the chance" to hunt Saskatchewan or Montana? And what game species would you hunt? While a .308 would work for moose, it's not quite as good as the .30-06, which might not be as good as one of the .300s. That said, you live your whole life and never get or take that chance, and you're throwing spendy ammunition and the beating your shoulder's taking makes lots of pre-season practice prohibitive - and you've got more rifle than you need for whitetails. Not a happy recipe.

If you're looking for ONE rifle, though - I'd opt for the .30-06. I'd never feel horribly overgunned for deer, nor undergunned by any means for moose. Of your list of manufacturers, the only two I have any experience with are the Vanguard and M70 (albeit, the post-64, push-feeders that are no longer sold as "new"). The Vanguard (mine's a .300 Wby) has met every one of my expectations. Tough, accurate, carries easily (light enough to trudge up and down mountain ranges). Oh, and it's cheap enough that you can afford to put good glass on it. If it has a minor fault, it's a trigger that's on the stiff side. Nonetheless, a dime will usually cover three shots at 100 yards.