You want/need heavier weight .30 cal bullets when you're hunting herbivores larger than deer. Think elk, moose, caribou, etc. If you legitimately expect to hunt game bigger than a deer and smaller than a grizz and a bison, you should be fine with any loading of .30-06. Loads for .308 peter out around 174gr, which are usually match loads like BTHP. Most .308 comes in 150gr.
In New England, the typical hunting shot is not more than 50 yards. Think treestand, whitetail deer, brush, forest cover. I have no clue what hunting Montana is like and Montana isn't even one uniform kind of geography - there's the mountainous western part, basically the Rockies, and then there's extremely windy plains, devoid of trees. From what I've read (and have no practical application with), a 600-yard shot isn't unheard of in Mountain West mountain hunting.
Ask yourself these questions:
*What am I hunting?
*Where am I hunting?
*What are the legal requirements for harvesting the game I want to hunt (put another way, what's the minimum bore diameter, what seasons are there, etc.)?
*Am I moving around or am I sitting still?
*Am I going about this objectively and rationally or do I want a gun because damnit, I want a gun?
To put these questions in action, if you're hunting deer in southern New Hampshire (in a town that doesn't ban rifle hunting) in a treestand, you're fine with a .270 or a .308 and you'll probably never need more gun in your hunting lifetime. If you're taking 600-yard shots on the vast, open plains of Montana at elk, you might want to step your game up to something beyond a .30-06, like say a .300 Magnum or a .338 Lapua.
I think the best "all things considered" option is a Savage 110 or a Winchester Model 70 in .30-06 or an AR or a bolt action in .223 if you're primarily a deer hunter and not trying to hunt anything bigger. If you are hunting something bigger, talk to professional guides in the area and see what they use. Around here, when people hire professional hunters to cull deer, the PH's use .223s.