Free: Contests & Raffles.
Bottom line, whatever difference there is, it won't matter at 50-100 yards. I'd take the one you are most comfortable with.
just checked a book I have and the 30-06 has way better #'s at just about all ranges w/180gr bullets. The .308 has a max velo. range of 165 yrds @ 2000/1599 for elk, the 30-06 has the same #'s at 365 yrds.