It seems that the jobs of clinical social workers and mental health counselors are pretty much the same, except CSWs earn a bit more on average. Also that a MHC has a Master's of Counseling while a CSW has a Master's of Social Work. So what is the difference?
The difference is licensure level. As you know scope of practice is dictated by state law. Social Workers have had great lobbying power through the National Association of Social Workers (NASW). This has included getting state laws passed with specific scope of practice for LCSW's. LCSW's have also have had a long history in establishing ties with the federal government, which is why the bulk of mental health therapists the federal government hires are LCSW's, Psychologists and Mental Health Nurse Practitioners. Mental Health Counselors has varying scopes of practices in different states in the U.S., and in some states you don't even have to have a specific degree…..they look at how many hours of certain curriculum you have had.
And of course, Psychologists also have lobbied against certain scope of practice that Masters level therapist with a counseling/or psychology can do in some states because they don't want Masters level psychology graduates reducing their demand as Psychologists. Which is why in some states, Masters level counselors (Licensed Professional Counselors, MHC's) cannot practice independently or diagnosis. In some states they can, and in other states they cannot. So it all depends on the state, for the scope of practice for MHC's. For LCSW's the scope of practice is pretty standard in that LCSW's can practice independently, and diagnosis mental health disorders.
If interested in doing comparison of scope of practice, you can go to the Association of Social Work Boards website.. http://www.aswb.org and click on licensure boards. Usually the social work licensure will be on the same website as other behavioral health professional licensure.