Decisions, decisions. You have a brilliant article idea. Do you post it to Infobarrel or Ezine Articles? There are other article sites but those two have the best user interface. Hubpages has too many restrictions on when the consider a link do-follow. So as for now I consider those two article sites the top two.
Personally, I use Infobarrel as Tier II and Ezine Articles as Tier III and my personal website as Tier I. Each tier points links to a lower tier(Tier I is the lowest) but never to a higher tier. I've experimented with having smaller sites as part of the tier but they don't work as well as article directories.
The main distinguishing factor between Infobarrel and Ezine Articles is the profit sharing. Infobarrel shares 75% of the adsense income whereas Ezine Articles doesn't. One way you can look at it however is that Ezine Articles is taking your money and reinvesting it in building the authority of it's site and therefore your articles. Many internet marketing guru's recommend that you reinvest your starting income. Ezine Articles does that for you. Ezine Article's has a higher PR than infobarrel and I've found that I get more views with Ezine Article's than Infobarrel articles even though I do more backlink work for infobarrel articles.
The other difference is syndicated content. Infobarrel wants your content to be exclusive whereas Ezine Articles allows your content to be syndicated. Controversy over how much duplicate content counts aside, every time your article is syndicated you get your backlinks and you get a profile link which strengthens all your ezine articles. Infobarrel having all exclusive, unique content has a benefit too. People have long speculated that unique content gets a bonus. If you don't know tips and tricks to mass syndicate your articles to a whole bunch of sites you may as well use infobarrel and get the unique content bonus.
Ezine Articles has their own eccentricities which can be a pain in comparison to InfoBarrel. Ezine Articles won't let you mention Ezine Articles in your article. If you look at Google Advanced Search, you can see that the page title(Ezine Articles) is huge in site ranking. By not allowing you to use Ezine Articles in the title of your articles you lose a potent ranking tool as ranking with an article with Ezine Articles in the title would be very potent in a site called Ezine Articles. Infobarrel does let you use Infobarrel in the title and even includes it's own category called Infobarrel help.
The other Ezine Articles eccentricity is that they limit the amount of times you can use a certain word per article. This can result in you having to go back and revise your article, making unnatural changes to get around work restrictions.
One final difference between Infobarrel and Ezine Articles is link strength. Infobarrel won't let you use links in the first paragraph, will insert internal links throughout your page, and if your links aren't on topic you have to put them in your sig. Infobarrel also requires 325 words versus Ezine's 250 decreasing the number of links you get per written content. Ezine does make you put your links at the bottom but won't put any links ahead of yours in the content. In terms of link strength, given the above and Ezine's PR, Ezine Article links are stronger.
Both Infobarrel and Ezine Articles have pro's and cons. I use both. You should too but I recommend using infobarrel in your tier II directly below your money site due to it's profit sharing.