All of the competitive surgical subspecialties are not DO-friendly: ENT, orthopedics, neurosurgery, ophthalmology, vascular surgery, plastic & reconstructive surgery, thoracic & cardiac surgery, interventional radiology, urology, plus derm, radiation oncology and medical genetics.
But TBH, all of those fields are extremely difficult for MDs to match into also.
Derm is probably out of the question for a DO. Oncology too, because oncology is one of the most competitive fellowships for IM grads and DOs are much more likely to do their IM training at a community hospital program instead of academic hospital. Academic hospitals offer the research opportunities and community hospitals (generally) don’t. Having oncology research is critical for a successful oncology match. (So are networking, audition rotations and top IM-ITE scores.)
DO-friendly fields include pediatrics, family medicine, IM, psych (though the competitiveness of psych has jumped recently), neurology, PM&R, pathology.
Procedural medical specialties (EM, OB/GYN, general surgery, anesthesia) and radiology are open to top DO students, especially if they’re not gunning for academic hospital programs.
CAVEAT–no one can predict what will be happening w/r/t to the competitiveness of specialties 10 -15 years from now. Specialties go in and out of favor all the time. Psych, EM and OB/GYN have become much more competitive in the last 5 year. Anesthesia, radiology and gastroenterology have become less competitive in the last 5 years.