You might want to use the search feature and type in "7mm08 AND 308". You'll come up with quite a few threads on that subject. Personally, I would go with the 7mm08. The 7mm bullet seems to make near optimum use of the 308 case - at least when it comes to hunting medium-sized game like deer. Check ballistics tables. Slightly flatter trajectory and low recoil are the benefits, although you might have a problem distinguishing between the recoil of a 7mm08 and a 308 blindfolded. On the other hand, you'll have a broader bullet selection for the 308 if that means anything to you.
Regards