I would think it depends on what kind of pain management fellowship at what program coming from what PM&R residency program.
I don't understand your exact question. As with any fellowship/residency with a good lifestyle and good income potential, pain management is going to be competitive. Talking to Anesthesia residents, it's competitive from their end, talking to PM&R residents, it's competitive as well. Neurology and Psychiatry are trying to get into the market, but I think most spots go to Anesthesia and PM&R. Psych (at least most I've met in pain) tends to go towards the chronic pain/narcotic dependency/psychosomatic pain type patient population. I know some neurologists specializing in neuropathic pain and headaches - but using mostly meds, some botox injections.