- If a post is flagged as duplicate, what happens then? In particular, what is different from casting a close vote? (I suppose that in both cases the post enters the review queue. Is the only difference that if the post is flagged, then it gets into the review queue with no close votes, so one more vote to close is needed?)
- For users who already have privilege to vote to close, are there any reasons why they might choose to flag a question as a duplicate rather than vote to close as a duplicate?
EDIT: I have found this post on meta.SE: Vote to close or flag exact duplicates? Or both?
The recommendation in answers there seems to be that if a user has sufficient reputation, voting to close is preferred to flagging as a duplicate, with some exceptions.
This would answer my second point. But perhaps somebody will have something to add to what's written there. And there still remains the first questions whether there are some important differences between the two things. (With the exception of the obvious difference that a low rep user cannot cast close vote, so if such user flags a post as a duplicate, no close vote will be added.)
I have to admit that when reviewing close votes I often open the question in a separate window. (To have a look at comments and answers already posted there.) If I see no close votes there, I get suspicious that this might be a review audit. This might influence the way I review the post, especially if it seems to be borderline.