Medical physics: if you want to go clinical get in a CAMPEP approved grad school program, work with someone who can give you access to clinical equipment like linacs, MRI, CT, PET/SPECT, ultrasound - doing preclinical research will not set you up nearly as well for job interviews and residency. Do your ABRs as soon as possible. Once you are ready for residency, whatever you do, do NOT go into an imaging residency - hospitals are outsourcing their imaging QA like crazy these days and you will end up a no-future job with 200+ travel days a year to places like Arkansas, upstate New York, Indiana and Canada. Always go for a treatment residency.
If you want to go research, don't go to a CAMPEP program, you will be doing a ton of course work for no good reason, find a superviser who is young and has a reputation for pumping out a ton of papers and getting their students done quick. Make sure you pick up a key skill such as statistics, monte carlo computation, C++ programming - something transferable that gets you on papers. Post doc is the name of the game and when it comes to post docs, it is go big or go home - if you can't get into a top facility in the States go abroad, don't commit to more than 2 years in any one place and your goal should be 1 paper every 6 months.