You raise a good question. Unfortunately, one treatment doesn't fit all who have back pain. Many scientists are trying to answer the question of which treatment is best for each problem. There are many areas in the spine that can cause pain--joints, ligaments, discs, cartilage, muscle, and so on.
But say two people do have the same problem exactly. Which is better? A doctor's counsel and advice or manual therapy and exercise? Researchers in Helsinki, Finland, studied this question. They found that patients got better in both groups.
Patients in the treatment group were more satisfied with the results compared to the advice-only group. The cost of care was less for those who only saw the doctor. There was also less sick leave used in the doctor-only group.
There isn't a simple answer to your question. Many studies are trying to find solutions to the chronic problem of back pain in adults. Stay tuned!