Both lawyer and nonlawyer representatives know Social Security's rules and procedures, the medical evidence you need to win benefits for your particular condition, and how to fill out disability applications. Nonlawyer advocates and professionals who work with SSDI and SSI applicants are actually more likely to spend a lot of time helping an applicant fill out the application and get all of the information the applicant needs. Some lawyers don't have time to help at the application stage, and will actually ask the applicant to call back after they get denied.
No matter what type of representative you hire, the most you'll pay is 25% ($7200 limit) of past due benefits (the lump sum of monthly benefits going back to when you first became disabled or applied for benefits). Both lawyer advocates and nonlawyer advocates are regulated by Social Security in the fees they charge, and they charge the same fees. Even disability advocates who work for legal aid agencies almost always charge 25% of disability backpay for their services. Both types of Social Security disability advocates are required to work on "contingency," meaning they get paid only if you win your case.
In addition, both lawyer and nonlawyer advocates can charge fees for out-of-pocket costs, such as copying and postage.