DOs have not been "traditionally" research oriented but things change. In fact, there are osteopathic physicians that do basic, clinical, and OMM research. Furthermore, just because research is not the main thrust of the osteopathic profession that does not mean that a DO can not do research, it is up to the individual. DOs are able to take every type of NIH and similar research fellowships that are open to MDs. DO/PhD programs are great for the serious researcher and the osteopathic profession needs progams such as these.
I completely agree that the osteopathic profession badly needs researchers. That's an understatement, but the OP has to think about their own professional life, not what the profession itself needs. I think the OP will find a difficult stigma attached to a DO researcher and as difficult as the physician-scientist lifestyle itself is, I'm not sure that's a good onus to take on. I would contend that there is a much more serious difference here than with just MD/DO clinical practicioners.
I am going to tread carefully here... As I don't think that a DO should mean a lesser degree or anything less than equality. But I think none has a point here.
If one is seriously interested in academic medicine, and has the GPA/MCATs necessary to compete at the top level for scholarships, etc, then a MD/PhD is probably better suited, if only because of the stigma that is attached to the DO degree. I suspect it would be much harder to obtain grants, to obtain a position in a non-DO hospital, etc...
There are many academic researchers that are DOs. Take a look at the DO/PhD program for MSUCOM; past graduates are very accomplished and successful! Lastly, in the world of research, speaking from experience, it is the quality of work that one does and publishes that receives admiration and respect. I have contacted many osteopathic physicians (DO and DO/PhD) that are involved in clinical, and dare I say basic, science research. They all say that these fears are, in terms of research,in the minds of pre-meds. Lastly, the NIH absolutely loves to give grants to physician-scientists, even DO/PhDs. Don't believe the hype!