I have seen handloads for the .243 in 115 gr but not in factory ammo.
Heres the ballistic comarison off the remington web site.
The .243 is in the new Remington load in 90 gr. and the 25-06 is in both 100 and 120 grains.

First off notice the .243 is better in coefficiency. It bucks the wind better than even the 120 gr -06
Second Velocity is a tad down at the muzzle but by 100 yds there already the same and by 200 yds it exceeding the -06
Energy is a tad down but the same by 300 yds, but the 120gr-06 is still a bit better but falls faster too.
Third trajectory- the .243 is shooting flatter from the get go.
Dont get me wrong the -06 is an excellent gun the reason I prefer the .243 is it does what the -06 will do, but also do what it cant and that is shoot 55gr, 60gr.and 75gr. ammo for varmints. These bullets tremedously excceed the -06 in long range trajectory.