270. If you ever hunt large meadows, it will shine over then 308 for trajectory. 150 gr bullets in it will shoot much flatter than a 180 in a 308, and will have somewhat more penetrating power. In the sub 338 guns, expansion is the key to killing. Due to higher velocity at any given range with similar SD bullets of similar design, the 270 will expand better than a 308 and shoot flatter for the same degree of penetration.
308 is the 270's retarded cousin. Shorter, fatter head, and a lot slower for the same job.
270 vs 3006 is a much closer discussion.
IMHO, 270 only really need 3-4 bullet weights. 130, 140, and 150. If you like shooting long range paper the 147 vld is a nice bullet, but that's a custom job...