Believe it or not, your goal with press releases, isn't to get backlinks from press release sites or insert keyword rich urls to your page. It's to raise awareness and get reporters, bloggers, publishers to notice your content or "news". Once they know about it, they may take action - link to you, contact you for more information, republish your release, or write their own story based on your release.
Don't expect PR sites to count for much, REGARDLESS of their domain authority. ezinearticles.com has a sweet DA of 95. Guess how much Google values a link from them ? PR sites were impacted by Panda just the same as sites like EZ were.
So needless to say I think you're looking at it all wrong. In choosing a Press release distributor pick one that can offer you the widest distribution for your newsworthy content. Unfortunately, you're not gonna achieve that with the free options. Why would you put your awesome content on sites that humans don't read anyway ?
In summary, stick with PRweb/Prnewswire and avoid putting targeted anchor text in your release.
-Just my opinion.