The 30-06 is the very best choice for the one-gun hunter.
Really? Of the 4 major US general purpose calibers (.30-06, .270, .308 and .7mm mag) as well as a vast array of less popular but similar calibers like .280 and 7x57 the majority of the time you could swap one for another and the hunter basically wouldn't notice. But in the rare cases where there is a difference, .30-06 is rarely the desirable choice:
- .308 is chambered in smaller, lighter, handier guns
- .270 and 7mag shoot flatter
- 7mag has higher sectional density meaning better penetration, more through shots, and thus better blood trails
- 7mag has better BCs for the same weight bullet meaning more retained energy at range
- .308 and .270 have less recoil
Really the only advantage the .30-06 has over the 7mm mag is the ability to load slightly heavier bullets, but as we saw earlier in this thread that's not enough to allow it to ethically address larger game like bison and the great bears.
The one-gun hunter would be far better served by one of the other three common options depending on their recoil tolerance.