270 in a feather weight or Mt. Rifle configuration, 308 in a carbine or mannlicher set up. Only time I would pick the 308 first is in an auto loader otherwise they are more similar than different. If you made me walk across hot coals I might confess the 308 is the more inherantly accurate cartridge. But this could be due to the scarcity of heavy barreled 270s where as there are many 308s in a target configuration.

After the 243 I shot a BLR in 308 and always hankered for a 270 which was probably from reading practically everything Jack O'Conner wrote. When I finally graduated from the 308 I went to the 7RM thanks to the writing of Les Bowman and Warren Page. I still can't pick a favorite but lean more to the 270 for the at least theoretical advantages.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli