well, it really depends on the other lighting in the room, which I am hoping to hear you have recessed lighting over this area as well. I like most of them facing up. But again it also depends on the style, the length and the projection of the fixture itself. For this reason i think it is VERY IMPORTANT TO PICK OUT THE SCONCES BEFORE PUT THE FINAL JUNCTION BOX IN

There are four recessed lights in the bathroom as well as a separate light in the shower so it will have plenty of light. We're trying to finish the rough in so we can hang sheetrock. I thought if I could decide between up or down light I would at least know where to put the junction box in height wise and would have a little more time to pick sconces. I have not been able to finalize that decision yet unfortunately but it sounds like I might need to do it soon.

Just have them poke the wire out, they do not have to install the box now, have them leave it poked out, they can adjust the height later.

can you post a picture of the space, or maybe the plan?

This is the layout, I'm not able to take an actual picture at the moment. The circles with the "x" in them is the approximate location of the recessed lights. I've also attached a picture of the vanity. Thank you!