If you wrote the article then you own it. As long as you link from the article directory back to the orininal post on your blog, the Google will take that as the original. My advice is to put the best and longest articles on your blog and use the article directories either for backlinks or as traffic feeders to your blog.

I'd put longer articles on my site and the shorter ones in article directories. If you're going to spend a lot of time writing a quality 500-1000 article, you might as well put it on your site. You are the one that deserves the long tail traffic that will come from that, not the directories.

I agree, if I need to create a quick site based around a keyword, i'll populate my pages/posts with content ranging from 250-500 words. My article submissions border on 400-500 words. Stallion has a good point about long tail traffic..you never know how someone is going to find your site through your content..you'd be surprised.

Let me look at this from a different perspective, I thinking about this. If you are thinking of getting link juice from high PR site, I would prefer getting it from an Ezine which rates a PR 5 or PR 6 and link it back to my blog ( given my blog has a lower PR ). Maybe I am getting it all wrong, I am bit mixed up as well... I would prefer having a very good article on an ezine which people would actually read as it is very much easier to get noticed there than on my own blog as I am not positioned the same way on SERPs for the same keywords. let me have your thoughts.