Depends if you want to concentrate on the primary care of athletes across the lifespan (FP) or are more interested in a specialist approach to rehabilitation of sports injuries (PM&R). I do know that there is a perceived bias among specialists in terms of referring patients to FP-SM. Orthopods and neurologists don't like to "refer down the food chain." They would rather work with physiatrists whose training they perceive as being on true "specialist" level.