Gypsmjim,
Reloading would seem to tip the scale in favor of the 30-06, in my opinion.
However, the 308 is a great round, and in the 15" barrel of an Encore, is virtually the equal of the 30-06.
In my 308 I was able to achieve just under 2600 fps (2588fps) with 150's, 2484 fps with 165's, and the only 180 grain load I ever shot was a Remington factory load that clocked 2422 fps. I would expect that the 30-06 would do about the same, or slightly better with factory ammo. Handloading should show a slight gain as well. I've seen 30-06 load data from Shooting Times that indicated 2700 fps with 150's out of the 30-06 Spr.
Accuracy of the two should be similar.
Now, if you're really after velocity, the JDJ version of the 30-06 is the way to go.
I've pushed 150's to 2915 fps, but this load was a bit hot. I consistantly get just over 2700 fps with 168gr C-T Ballistic Silvertips. I've only briefly shot 180's, and stopped when I reached 2550 fps. 180's made my scope shift slightly even with the T'SOB mount.
Check out
www.sskindustries.com for information regarding the '06 JDJ cartridges.
Regards,
Rog