Why just consider those two?
Having played a bit with different calibres over the years I have come to the conclusion - and before evryone starts it's just my opinion based on my limited experience - that the ideal velocity to get acceptable trajectory and an acceptable level of carcass damage is somewhere between 2900 and 3000 fps. The ideal bullet weight is about 120 grain. Go any faster and any heavier at that speed and the additional energy you gain just comes out the other side. Ideally you want a high BC bullet as trajectory is easy to predict but wind deflection is much more difficult. The 6.5's are particularly good. Unless you are shooting Boar in this country you need no more power.
I have ended up with a 6.5 Lapua running 2960 fps with a 120 grain bullet with .458 BC. It puts down everything from Muntjac to Reds with great efficiency, little recoil and is cheap to reload. With only 39 grains of powder I also use it without a mod without my ears bleeding! It's much more balanced to carry as a result. I have had .308, .270, 25.06, 6mm06AI and 7mm Rem Mag. This is the best all rounder. If you wanted to go off the shelf a 6.5*55 will be pretty close, loosing only about 150 fps. You are also likely to be more accurate as the recoil is much more civilazed than either a .308 or .270.
There is such a thing as too much gun. Just my opinion.