Two things I look for in a mirrored cabinet over the sink: centered over the sink and recessed. Recessing can be a problem as that is likely where the vent pipe goes. In my bathroom, I had to build the wall out to be able to recess the cabinet. I don't think you'd like a large single panel door if the cabinet gets very wide - you'd have to back away as you opened it with the typical vanity depth and if it was left open, you might bump your head into it, especially shorter people and children. Considering it contains glass, that's not a great idea.