Looking at my Barnes reloading manual #2, ballistics show the 270 shooting the 100 gr xfb (now replaced by the tsx) slightly flatter than the 25-06 out to 600 yds, but the difference is negligible.
My Barnes manual lists bullets from 75 gr - 115 gr for the 25-06, the same range for 243, just more speed with the 25-06. 270 bullets range from 100 gr - 180 gr, that would give you more versatility.
I did a little research on the 25-06 a while back and if memory serves me the 25-06 will burn up barrels relatively fast, that may be a consideration.
They are both fine cartridges, accurate and flat shooting, but I would opt for the 270.
Good Luck,
Karluk