Something that just occurred to me is that I'm not sure when a vote to close a question should be used as opposed to a downvote. It seems that every case where I would downvote (the question is vague and unclear, argumentative, etc.) is also a case where I would vote to close. In fact, surveying my downvotes and my votes to close, it seems that in almost every instance since I could vote to close that my downvotes were accompanied by a vote to close. But then that just seems a bit redundant.
Since I've only had the vote to close privilege for a short while, I think that maybe I haven't picked up on the subtle differences here. Is there one? Or for users with the privilege to vote to close will the legitimate reasons for a downvote coincide with reasons for a vote to close?