To reopen or close a question it needs 5 votes cast in favor of the suggestion (or a mod uses their cheat codes). When I review a question that has been nominated for reopen or to be closed, whether I say specifically "No" to the suggestion by choosing the "keep open/close" button or say "I can't decide on the matter" by clicking skip, the question doesn't get my close/reopen vote, so it seems to me that it doesn't really matter, or to quote the street fighter movie:
If good men do nothing, that is evil enough
Is there any difference between choosing "Keep question open/closed" and "skip"?