Depends on if you want good light or something stylish. I like lots of light, so I would go with 6 globes pointing down on one bar in the center of the vanity. That is what I ordered for this home, but didn't get it. I got one bar with 3 lights over each sink and the lightening is terrible.

Conventional wisdom is that side lighting is more flattering. I find it really depends. Downlighting can be fine if it is a fixture that bounces the light off your face (so not too high) instead of casting shadows below your eye sockets. This time, we're doing some sconces that sit directly on the mirror, but haven't gotten them installed yet.

As stated above, side lighting is more flattering and with 200w in my old bathroom with hanging sconces, it was like an operating room! Don't want to talk about what I have in the new and improved bathroom :o but I will say what's going in DH's bathroom. He said he doesn't care about "flattering"...he wants to SEE. His eyes are 56 years old. His vanity is 36" long. Mirror will most likely be the same. We're going with a 3 bulb (100w each) fixture above the mirror. I doubt I'll do 300 watts in there. I think 180 will be plenty, but, the room will be on the dark (aka manly) side especially if we do a wood ceiling, so more wattage may be necessary.