I guarantee you that they (residency directors) prefer the USMLE. If you are a DO and want to do ENT in the army, you are shooting yourself in the foot if you do not take the USMLE. You also better bust it on part 1 to make up for the stigma of a "DO" degree. Nothing against DOs (I personally know 2 that are ENTs and they are very good), it's just the way it is.