Any of them will work just fine for what you want to do. Lots of guys use all of them.
A 30-06 is the most flexible. Has factory loads of 220 grain bullets for the deepest penetration on moose of these three, and you can start with managed recoil loads that have the recoil like a 243 Win. The usual load is 180 grain bullets, good for deer and elk.
The 30-06 and 270 Win shoot practically identical in the mid bullet weights. The 308 Win was developed for auto loaders; its cartridge case is just a little shorter than the 30-06..
Outdoor Life 50 Top Guns in Last 10 Years
www.outdoorlife.com/photos/gallery/guns/2011/05/best-hunting-rifles-decade
Stevens 200 270Win $320
Marlin XS7 308Win $350
Weatherby Vanguard 30-06 $500
10 Quality Hunting Rifles for Under $500
http://www.gunsandammo.com/2012/03/08/10-quality-rifles-for-under-500/
Hunting Guns: From Your First Rifle to a World Class Battery
http://www.chuckhawks.com/hunting_guns.htm
Bolt Action Rifles for Dangerous Game, The Rifle Stocks
http://www.chuckhawks.com/bolt_rifles_dangerous_game.htm
http://www.chuckhawks.com/grizzly_cartridges.htm
Recommended Riflescopes
http://www.chuckhawks.com/recommended_riflescopes.htm
http://www.chuckhawks.com/scopes_price_class.htm
http://www.chuckhawks.com/compared_dangerous_game_riflescopes.htm
Prime Questions: list your priorities, rank them to your mission
1. How far is your target--max effective range
2. How tough is your target--remaining energy & bullet construction/type
3. How easy to feed the rifle, ammo & component availability
4. How easy to carry & move the rifle, weight, mobility
5. How easy is to make the shot, recoil, trajectory, wind deflection
Not important: lightest bullet with highest muzzle velocity
http://www.youtube.com/watch?v=pwG-D0HjCBQ
BrassFetcher: bullet performance in ballistic gelatin
http://www.brassfetcher.com/
The Box O' Truth: ammo penetration through various barriers
http://www.theboxotruth.com/docs/sitemap.htm
Terminal Ballistics Research: cartridge & projectile performance, game.
www.ballisticstudies.com/Knowledgebase/.30-06+Springfield.html
Heavy bovine game: .308 to .50BMG
www.ballisticstudies.com/Knowledgebase/Heavy+Game+Cartridge+Overview.html
Hope these help. Shoot safe.