The 30-06 can shoot bullets heavier than the 308 Win,
I hear this all the time, and it has always irked me. Its a (possibly) valid opinion, but as a fact, its simply not true.
Any bullet that can be fired from a .30-06 (or for that matter a .30magnum) can be fired out of a .308. Period. The difference is what speed you can get. And what speed you, personally, consider good enough. Much is said about the advantage of the 06 over the .308 with heavy bullets, but the .300 magnums have the same advantage over the 06, and I never hear about that...
A .308 with a 200/220gr bullet is basically the same as the .30-40 Krag for speed. And the Krag has taken untold numbers of deer, elk, and moose (as has the .303 British and the "lowly" .30-30). The biggest grizzly on record for the continental US was taken with a Krag IIRC. Enough performance to take the game is clearly there. Enough performance to satisfy the shooter, is another matter.
Each has enough "oomph" to do the job well. The practical differences are personal. How well you shoot each rifle, how accurate they are in your hands, how well you tolerate the recoil, etc.
At even the longest practical ranges, the difference in drop and wind drift between all three is a matter of a few inches. If you can accurately compensate for drop and drift with one, you can do it for any of them just as well. its just a matter of learning how much is needed for each.
Where the faster rounds have the advantage is covering for our mistakes. Faster means flatter shooting, which means that if we make a mistake in estimating the range (or the wind) the faster bullet might still strike in the vital area of the game, while the slower one, with a more arched trajectory might be too low, or even too high, depending on if our range estimate was too low, or to high.
But that is a matter of shooter performance, not the cartridge or bullet performance. Pick the rifle, and caliber you want, and like best, for any, or no particular reason, use it correctly and within its capabilities, and yours.
Bigger (alone) isn't always best. Sometimes, good enough is well, good enough.
Good luck!
always been impressed by moose...even Bullwinkle
anything that can carry a 5 foot rack, and slip between trees a foot and a half apart, at speed is impressive to me!