I can speak from both perspectives...I have an MSW and have practiced as a clinical social worker for several years. I also have a BSN and am currently in an MSN (Psychiatric Mental Health Nurse Practitioner) program. With regard to income, with a few years of experience as a social worker (depending on the area of social work that you are practicing) you will likely make about the same as an ADN/BSN working on the floor.
You have to ask yourself several questions in terms of making this decision. What are you interests? What are your motivations? Where do you see yourself in 5 years? If you are planning to pursue nursing or social work simply for the money, you are going to be disappointed. Both fields have a significant overlap and require a great deal of emotional energy - essentially, you have to have an interest in nursing or social work.
In my personal experience, I found that my MSW and my BSN have been a nice blend. I have found my MSW to be a great decision in terms of personal satisfaction as well as providing a comfortable lifestyle. I primarily do psychiatric evaluations at several local hospitals and then do mental health assessments at an outpatient agency. I have also done some teaching in both social work and nursing programs
. Immediately after nursing school I knew that I didn't want to do floor nursing (I have great respect for bedside nursing, just found that it wasn't a good fit for me). I have the ability to make my own schedule, work very few nights/weekends/holidays and can take vacations whenever I like. As someone else mentioned, social work offers a certain quality of life that can't be found many other places.
As I have continued on in my MSN program, I have realized that this too was a great decision and will ultimately allow me to blend all of my passions and interests together. I believe that I feel that my educational endeavors have been good choices not because of the financial benefits, but because I have found a career path that is something that I find satisfying.