For medium/light 70 grain bullets, there is a 99% chance that the 1 in 9.25" twist will shoot them exactly the same as the 1 in 10. There is a 0.9% chance that it will shoot them worse than the 1 in 10, and a 0.1% chance that it will shoot them better than the 1 in 10.
1 in 9 or 9.25 is good for ALL bullet weights that the .243 comes loaded in. It is only with 1 in 10" and long 100/105/107s where you might get some instability fliers (or with long all-coppers past 80 or 85 grains).
Therefore, when in doubt, 1 in 9.25 is the better choice, all else being equal.