My opinion as a DO who matched into PM&R last year:
Mostly agree w/ Jagger -
You will find a fair amt of DO residents and attendings at all of the top programs in the country. It's hard to say if there is truly an advantage, but I feel that it's a reasonable assumption to say that there is no disadvantage
There are only 2 dual programs that I am aware of - MSU and Nassau. All of other 80 or so programs are AGCME. Formal manual medicine training in PM&R is not nearly universal, but its generally looked upon in a positive light and some programs have faculty who use it in practice.
As for AGCME ortho...not so much.... most DO's who want ortho go into AOA (DO-only) ortho residencies. Even the few who may have been strong enough applicants for AGCME ortho programs find it extremely difficult to pass up an AOA spot (as our match comes 1st) for an outside shot at theirs.
Hope that helps
If you have more q's about PM&R you may want to check out the PM&R Residency forum- lots of helpful and knowledgeable people there