Col. Boddington, in his book called The Rifle, said that as a practical matter, he never saw any difference in killing power in the field between the .308 and the .30-06. In other words, it was all theoretical. Having hunted with both rounds for 40 years, this is my experience as well.
And please, don't start talking about which would be best for Grizzlies. :-) Male fantasy stuff.
Aside from the .308, my second choice would be the 6.5 Swede, for the reason listed by another poster above.
The 30-06 is an excellent round, but just wouldn't be my first or second choice.
The .260? Well, the factory loads are limited, and I'm just not sure it is here to stay. A great round, but never caught on like it deserved. The 7mm-08 would be a far better choice.
Mannyrock