Need help choosing a doctor? Is orthopedic or physical medicine doc better for back pain?

No right answer. There really is no right answer for this question. While an orthopedists and physiatrists training may vary, both doctors are able to obtain the latest information on the most effective treatments. Physiatrists are not surgeons. 99% of back pain problems do not require surgery in my opinion and the track record for back surgery for back pain is not great. However, either specialist can help.
Back pain. Depends on the physician not the specialty. Excellent back specialists in both specialties. Would ask around, check health grades, ask you primary care provider.
Either. Both are trained for back problems. Find someone who listens to your complaints and takes appropriate steps.