Flip a coin for use on Whitetail... I have one of each and love them.
The + to the 257BOB is the lighter 75&85gr varmint bullets are nice for V-hunting.
The + to the 7mm-08 is that you can load a little heavier bullets like the 150 and 160's which make it just slightly a little better suited for Elk.
Although the 7mm-08 with 100gr'ers can be used for varmints and the 257Bob can be used on Elk with no probs with the right bullet.