The differences between Allopathic EM programs and DO EM programs can be extensive, but they seem to focus on a few things.
Allopathic EM programs are recertified/approved by the Residency Review Committee (RRC) which puts each program under strict guidelines for research, attending supervision, didactic time/week, academic projects, and exposure to peds EM/ trauma etc. In the DO world, it has far less strict guidelines.
Few DO EM residencies are at level 1 trauma centers and virtually none have the same academic guidelines found in allopathic programs. Even fewer have board certified, EM residency trained docs as attendings.
Allopathic EM programs have worked hard to legitimize the profession...to make it a complete specialty filled with academics/research/clinical expertise. It is taken VERY seriously.
Some programs have dual accreditation, and those are strong programs.
But as a whole, DO programs do not "suck". They just simply do not offer what 90% of MD EM programs offer. And, all else being equal...a candidate from an Allopathic EM program has a heads up on an Osteopathic candidate for the same job. It is competition.