with the same weight bullet, same barrel length, the 270 produces the highest velocity, BUT, the 25 goes down to 75gr V-Max, and 85 gr Btsp, while the 270 low end is 90 gr with not as good BC. Also, most 270 barrels are 22", most 25-06 barrels are 24-26 inches. Using a slower powder that extra 4 inches of barrel could mean 125+ FPS gain in muzzle velocity. My book (Lyman 49) shows an accuracy load of 3401 fps for a 270 90 gr HP, and 3740 fps for a 75 gr V-max. If it was going to be your only gun I would say 270, but for light, long range stuff, go with the 25.