To my knowledge (and I'm not the best at this even though there are people that I work with who specialize in SEO) Google penalizes duplicate content from the same source. So, if both articles are within the same domain (or, likely, subdomain) then Google says, "Oh, this must not be that important because it appears several times on this site. Might be a re-usable content block or something."
The benefit of writing your own articles would be that you're probably not submitting ALL of your content to an article directory. Having your own, personal articles would be a means of getting visitor traffic to "stick" on your own site.
