I would also buy whichever is in better condition. If it’s a toss up the 30-06 does have a wider range of factory loads available. 125-220 grains. Most guns a 308 would be a short action, but on a 760 they’re all the same action anyways.
They are both 30 cal but i prefer the 30-06 because I shoot 180 gr bullets . The 308 is not as accurate with the heavier bullets. 308 is great with 150 and 165 gr but I like the 30-06 180's better. But that is my preference. I know lots of guys that shoot 308 and 30-06 using the 150 and 165 gr in both and they love them.