-Academics, employee model, and/or non-RVU based PP = all make the same (all partners make same in PP). Bonuses for more call/less vacation (ex. IR, sometimes neuro)
-RVU/production-based PP = neuro, MSK usually the most due to higher volume of high RVU studies but really whomever works the most gets paid the most
-IR has the least RVUs but they are paid same/more due to amount of call and because they are a necessity for a hospital.
-Breast likely makes the most/hr since they can negotiate no call/weekends sometimes as more and more rads don't want to do any breast stufff
These are generalizations but roughly how it is. Keep in mind nominal value per year is not the same as $$$/hr.