Last I knew, VA paid PM&R base specialty less than anesthesia. Other than that it's all over the place. AMGA has consistently listed "non-anesthesia pain" as earning more than anesthesia pain. Probably because the PM&R docs work harder and are better looking.
Variability between jobs/region etc is probably a far larger spread than any consistent difference in pay between the 2 base specialties. For the most part, your review of local anesthesia pain salaries are a good estimate for PM&R pain in the same region. The anesthesia data is probably a better representation based on the number of responses, as there are far more anesthesiologists than physiatrists.
The market looks great where I am. We could use more good docs. If you want to be in NYC/west coast or decent parts of Florida, you'll probably take a serious hit financially.
My anesthesia friend tried to get me to join his private group, but I didn't think the relative autonomy was worth a 40% pay cut. (This was likely more related to SOS hospital-based employment and a potential low-ball offer than specialty.)
Of course, anesthesia can take call, etc. and make more in their base specialty than most of what PM&R could make peripherally. Work comp/medicolegal can be a headache, but pays me more per hour than everyday "Pain" work.
I often describe my practice as 75% the same as my anesthesia colleagues. I quit doing EMGs a few years ago. I have a few legacy SCI patients (who see a partner for general issues). I still do amputee care because no one else around here will, and those patients end up getting a lot of injections. I was a director at rehab facility (2-4 hrs/week) for several years until it wasn't worth the time away from the office. I probably do more U/S than most, but don't fall into the diagnostic circle jerk described above.