It can be done both ways. I like the tile down first then if the wife decides she wants a different vanity you know it will happen they change their mind like they change their clothes. will look ok and you wont be trying to patch it up. nice clean look and easier to do with more room in the bathroom. My wife has changed her mind at least 6xs today on where she wants the dining room and living room back n forth:confused1: Next week when she sees a vanity with legs she may want one then yo will wish yu hat tile under there.