A light in the middle of the room can be good for overall ambient light, but you need light at or near the mirror for seeing your face et al. I'd just do a light above the vanity, assuming that's possible -- be sure you get plenty of lumens from whatever you pick.

Generally for any kind of up close activity in a bathroom you would want lights directly above you. A light in the center would probably not provide adequate light, nor would recessed lights. You could potentially have both a center light and a light above the vanity- depends on room size.