What is the difference between submitting my site to rss and blog directories

[needseohelp]

What is the difference between submitting my site to rss and blog directories

I am running on wordpress/thesis when ever a blog post or page post is made is it not being submitted to rss directories automatically so why submit to more of them.

Any reason to submit my blog to blog directories any seo benefit to this and how is it different.

How should I submit to blog directories -- should I target specific ones or submit to all of them. For purposes of seo and back links any benefit to submitting to blog directories if none is there any other benefit ?

[sukhiseo]

Rss give latest update about your site but directory submission create your blog traffic and generate visitor.

[mkowlowitz]

Rss give latest update about your site but directory submission create your blog traffic and generate visitor.

Some of them I notice cost money. How much better are the paid ones compared to the free ones?

[mkowlowitz]

Quick question: when you add your site to an RSS directory, do you have to ping that directory to let them know your site has been updated or do you just ping blog which lets all the directories know? thanks