(...in our strategy for syndication)

Since you've created your syndication quality article and you're submitting it to multiple websites anyway, there's no reason why you should not submit the same article to some of the more common article directories. Remember, we're not looking for back-links, since they're pretty worthless from these sources anyway, and we're not expecting much in the way of direct traffic, but it is possible that your article will be found within a directory and syndicated, and that's what we're looking for.
Incidentally, once you've been doing syndication successfully for a while, you may have collected some fairly high-profile publishers who're using your work. In this case, you might not want so submit those same articles into article directory sites, rather, keep an element of scarcity so the higher profile websites have something with a little more exclusivity from you. But for most of us involved in syndication, submitting the articles into the larger article directories shouldn't cause a problem. So who are they? - [get the full list when you download our article marketing guide here]

Obviously that's quite a task, manually going through and submitting your articles to so many directories. You could of course just focus on the top 5 or 10, or you could automate the task.
There are a few well-known automated article directory submission programs around, one of which is AMR (Article Marketing Robot). You can select your article to be published into over 1000 directories, and I'm sure many of the top 50 listed above are contained within their database. But you need to be careful if you're using these types of automated tools, it's better if your rate of submission is slow and 'natural' looking.

If your modus operandi is to gain back-links, then original content might be better. But we've already discounted that as irrelevant so your main purpose should be to attract syndication. In this instance, spun articles are not going to be of the requisite quality needed to attract syndication, so it's better to submit the same copy to each directory.
For most of my own syndication efforts I don't use AMR or any other automated tools. They get the job done but I rarely see any benefit from these directory sites these days, so why bother? [learn why when you download our article marketing guide here]