I can't believe nobody has mentioned the duplicate content filter here yet.
More often than not, Google tries to see only one version of the same article, and dismisses the others. Try to make your articles considerably different from eachother.
Also - reputable article directories, the ones that Google trusts the most (and where you get the most link juice), will check for duplicated content before putting the article live on the web, if you are using spinned/rewritten articles, submit to these first (like ezine articles), so there is no duplicates out there for them to check.
You MAY get some link juice from duplicated articles though, even if they are filtered out to the 1000's in the SERPS, G still does usually crawl them, and follow the links in them.
I used to spin articles, using SENuke & the best spinner, but I found the link juice & worth of the articles was minimal. From my experiences, it's better to take the time to write ten quality articles (that have a chance of ranking & driving traffic), than to spam the same one to 1000 spammy article directories.
Experiment though, and draw your own conclusions.