Unless your research interests lie in something related to the skeletal system, avoid going the DO route. Academic and research medicine is a highly prestige conscious field, and having to put "DO" on your resume will not be a positive thing. This is because, fairly or not, many doctors still view osteopathy as a pseudoscience, and see osteopaths as people who couldn't get into a regular medical school. (I don't particularly agree with these sentiments, but many doctors still hold them.) Also, you'll be at a significant disadvantage in applying to mainstream residency programs.
I know I'm gonna get flamed to death for what I just said, but I'm simply telling it like it is.