On whitetail deer, there is no real difference as far as I am concerned. However if you hunt larger animals like elk or bear, and use 180 grain or larger bullets, the 30-06 starts to have a bit of an advantage. In the .308, I think that the long 180 grain bullets start impeding on case capacity so you start giving up velocity due to reduced powder charge. I myself choose the .308 since I live in the southeast and don't hunt elk or bear. The 30-06 produces about 100 to 200 fps more than the .308 in most loads. The .300 Winchester magnum produces about 100 to 200 fps more than the 30-06 to put that in reference.