Personally, I think a story should be the best it can be before you start subbing (not that I've always done that or anything), so submitting to one market at a time, versus 5, to ensure that you get 4 extra chances to edit seems a little silly.
But, I usually only submit to one market at a time, because I have a top-down system. There aren't 5 markets that I'd be equally pleased about if I were to be published in them. I have my favorites.
So, let's say you send your story out to 5 markets-- two you really love and 3 you feel so-so about. A month later, one of the so-so markets gets back to you with an acceptance. Hooray! Except, you haven't heard back from any of the other markets yet. Selling shorts isn't like selling a novel--typically you don't sit around waiting for the best offer. You sell the rights to the first bidder, not the highest. It's unprofessional to write back and say, "Thanks, but I'm waiting for my preferred market to respond" or, "Thanks for the offer, but a better market has decided to buy it."
Of course, if all 5 markets are the same to you, it’s a moot point.