Hi Pam

Someone else may jump in here and correct me if I'm wrong but in my understanding an eZine is something you set up and distribute to subscribers, like an eNewsletter. It might contain more than one article, and is a way to reach out to current contacts and others who've signed up to find out what you have to say. While article submission is where you've got a great article you've written and want to distribute it to a wider internet audience - by submitting it to the article directories it's then indexed by the search engines and will potentially turn up for those who are looking for the very information you wrote about. With a byline including information about who you are and what you do, as well as a link to your website - they may be interested enough to follow the link to learn more about your services... etc.
I'd say that ideally, you'd do both - if you've got the time and inclination. The more marketing and outreach the better!
If you check the directory here on the site [it's listed in the main menu at the top of the page] there's a category in VA Resources for Article Directories that you can submit to. Hope that helps!