if you seek the simple/ordinary benefits; applying is easy. If there are complicating factors, like disability etc, that's another story, and its possible that without an experienced attorney, benefits will be delayed or denied.

http://www.socialsecurity.gov/pgm/retirement.htm

If you are asking the difference between a so-called 'advocate' and an 'attorney,' I suspect the main difference would be between the relative records of success between individuals you are considering.

tend to get it done most effectively and efficiently. Advocates not so much.

They do get a percentage of your back pay, but that's probably worth it, as so many who apply without them never get it all.

They do not get any part of your monthly benefit. I signed up with an attorney from the beginning. I got approved the first time, but didn't get back pay so he didn't get anything.

and before they have a lot of back pay to turn over to the attorneys.

Glad you were able to get the system to work for you. It is a nightmare that takes years for some people.