This writer is not familiar with the exam and cannot comment on the certificate as an indicator of competence. Most states do not have such programs so the lack of a certificate should not be taken as an indication of lesser competence. An attorney does have a license to protect and is subject to discipline for gross incompetence or neglect. This may give you some comfort. An attorney can represent a person before the Immigration Service.
All notices go both to the attorney and the client.
Attorneys can call upon colleagues, law libraries, and other sources of expertise that may not be readily available to others. Some attorneys have smaller, boutique practices with somewhat higher fees but with specialized, individual attention given personally by the attorney to each case. Others operate a kind of assembly line, volume practice with lower fees but less time and attention given to inquiries and cases. Communication may be through a receptionist or paralegal with references to clients by case number rather than name. In some of these offices, the attorney is rarely seen after the first visit.