Best comment system to use with Wordpress for SEO

I'm looking for opinions. I'm not sure there really is a difference when it comes to SEO benefits. I started using Disqus recently though and it seems to have helped in the SERPS, Facebook comment plugins seem to be the worst and may have a negative effect. Feel free to chime in.

Here are the Wordpress comment systems I know of

• IntenseDebate
• Disqus
• Livefyre
• Facebook comments

You forgot
* CommentLuv

Seems like the most popular way to encourage non spam comments with keyword link rewards for top commentators

for me disqus is the best till now

Disqus is the one personally