I have been working with a DO pediatrician (shadowing with him), and he did an MD residency. He said it was "getting the best of both worlds" -- because he still learned the values that a DO school had to offer, but then got to work closely with other MD's during his residency (which mirrored what he has to do now as an attending -- collaborate with both DOs and MDs). Plus, he said that the MD residents he worked with were really interested in learning about the OMM skills he had acquired in DO school, and truly thought that both types of residents (himself and the MDs) had that much more of a memorative & learning residency as they worked together.
Its what I plan to do as well-- DO school and MD residency. I don't think you'd be giving up anything or "selling out" as far as being a DO... just having the chance to experience more.👍