Blah. What a stupid simplified answer. 🙄 I've been playing with this idea in my head, and I've been speaking with residents and program directors and attendings throughout Philly, and here's what I've come to realize...
Take the USMLE if you feel CONFIDENT that you will score well. Being on an unquestionable even playing field with competitive MD students can fail if you don't capitalize fully on the opportunity and perform well on the USMLE. The correct answer is that most PDs in traditional DO regions are fine with the COMLEX. The military is fine with the COMLEX as well. Where you are going to run into issues is PDs that don't typically see DO applicants and therefore do not know what a COMLEX score result truly means other than the printout and score in front of them. In general, the policy goes with job apps that if you can give them a reason to exclude you, they will, so removing one variable from your application, as long as it doesn't become a weakness in your application (you can't hide your results!), is probably beneficial. However, as I've said it's regional and based on whether the hospital is historically "DO-friendly". It has less to do with the specialty per say, although if there are fewer applicants (FP, Peds, some IM) they are less likely to throw applications out.