If the installation instructions say they can be mounted in either direction, then no, there's no "right" way.

Personally I like them facing down only because it is easier to dust inside and change the bulbs!

IMO lights should light up the area that needs light which is not the ceiling.

Clent Joseph Dela Perl, please elaborate on what you mean by move on the side ? Why shouldn't they be over the sinks ? Thanks.

I'm with Debbi. It's less of an issue inside, but I absolutely detest things that aren't open on the bottom for outside. Still I hung my vanity features with the globes facing downward. The ceiling doesn't need light.

In this case, I think the lights up would be too high and create hot spots on the ceiling. The way you have them centered creates pools of lights on the sink. You should take a photo at night with the lights on. Also test flip them if you are not convinced.

CJDP is correct. You don't want a light glaring you right in the face.

Bathroom lights should be at face level and off to the sides so that you have even light on your face with no harsh shadows (especially under the eyebrows and chin).

That vanity needs 3 fixtures--two pushed to the walls and one in the center. And lower.