I think it depends on if you keep the original front sight post.
I think the high mount is needed to get the aimpoint over the top of the front sight post so you can see the dot better (or at all). If you have a front sight that you can flip down, I think lower is probably better.
Not an expert in this... just went through it with an eotech on an A3 a couple months ago and going through it right now with an aimpoint on another gun.