Been done to death but both are great and would work.
.30-06 has wider range of bullets, is arguably a little better on big game like moose, elk and bison.
.270 has an advantage at long range due to better BC bullets at a faster speed than a .30-06. It has more energy down range. 95% of hunters would never shoot game far enough to see a difference. It also has a little less recoil than the .30-06, but both are pretty mild in that department.
As for me, I own a .280, better bullet selection than the .270 and better on the prairies than the .30-06.