I'm seeking to advise my son, a current straight-A undergraduate physics major, who is considering applying to a graduate program in medical physics that, surprisingly, only requires the generic GRE exam - Not the physics GRE. From his past experience with taking the SATs and knowing he's an absolute math nerd/genious, I know he can do quite well in the math and analytical sections but his verbal skills have always lagged. I can predict his GRE will not be great in the verbal section. Might it be advisable to take the physics GRE anyway just to bolster his qualifications?
I am currently in a medical physics PhD program. My background is in "traditional" physics.
Medical Physics programs are completely different from that of traditional physics programs. Most medical physicists (even PhD-level faculty) probably wouldn't do well on the Physics GRE (which is challenging for a junior/senior/grad student). The ABR exams which medical physicists take involve freshman-level physics, at the most. No math beyond calculus is needed in medical physics.
In short, if you're son is set on entering medical physics, a high score on the PGRE won't help; the material is simply not relevant to medical physics for the most part; that is why they are not required on the applications. Some of the accepted students might not even be have a BS in physics. (They might have BS in bio, EE, etc.) If your son wants to practice in the clinic, he will almost certainly need to graduate from a CAMPEP-accredited program (although the accreditation itself is a joke, in my opinion).
The general GRE isn't taken too seriously by the admissions committee. If you have an undergrad degree in science/engineering, it shouldn't be too difficult to get a high score on the quantitative part (with prior preparation, of course:). If I were your son, I'd put some emphasis on the quantitative part, but a lot of emphasis on the verbal part, since it sounds like that's where he needs the most help. An unusually low score on the GRE might automatically weed him out of consideration.
As for medical physics in general, you should be aware that the entire field (academically and professionally) is in a unstable phase at the moment. There is a huge variance when it comes to what programs emphasize, funding, residency programs, etc. Like many other science/engineering disciplines, medical physics programs produce a lot more graduates than are actually needed to fill jobs. Unfortunately, finding hard data is tough. The program websites, brochures, AAPM website, etc. don't seem to have their facts straight.
I hope this helps. Best of luck to your son for whatever he decides to pursue.