Between .308 and .270, it depends on what game or targets you plan to shoot with it, at the the smaller end or at the upper end of game size, and at the ranges for targets.
The .270 is more versatile than many put it to use. You can load down 90-gr bullets like a .243 for varmints, and 150-gr Swift or Barnes and shoot Eland dead in their tracks.
But if you plan to shoot larger deer, the .308 with 130-gr shoots very flat to 400 yards, and has good bullets for big deer, elk, boar, etc. And it has the match bullets to shoot out to 600 and 800 yards in the right rifle.