A further issue is bow speed. I think if you are only getting say 202fps with ACE then you will drop below 195 with X10, this I think will be too low. If you can get X10's over 200fps and preferably nearer 210fps then I think you will find it excellent at all distances. Arrow design is a trade off. We all know that you want as thin as possible.
Weight however is more dependent on the archer and their setup.
A heavier arrow is in theory more accurate and stable, it will also have more kinetic energy than a light arrow. The light arrow does however have the flatter trajectory and more absolute speed. In perfect weather if both arrows are tuned the same I believe you will score the same with both arrows. In a breeze the X10 comes into it's own. I would also like to see the physics explained that can make an arrow good at 70m but not at any other distance.