My advice would be go to RFU if the tuition difference is not too great. Now my main reason for this is not to knock DO schools, which will give you a great if not better education than you might get at some MD schools. I think OMM could be a great tool to have....
However if you want a tangible reason as to why MD over DO...it's simply residency options.
Research publications indicate that Residency slots have been capped since the late 90's. While the numbers of DOs in ACGME residencies has increased in the past 10 years significantly, the number of MDs graduating is concurrently starting to increase along with DOs. As a result, it seems gaining a residency will be more competitive for all physicians (DO,MD, FMG). However, most ACGME programs will favor MDs, as a result there might end up being significant amounts of DOs and FMGs that do not match at all.
My guess is that the pecking order will hold true MD > DO > FMG, and mostly FMGs will get squeezed out.
I would say that this residency concern would not matter if you are dead set on primary care, pmr, psychiatry....However if you want a top residency ROADS, then go MD. You could make the argument that DOs have osteopathic residencies for these tough specialties, but i THINK many good fellowships will not take on AOA residents? Additionally, there are many less osteopathic residencies and this will limit you on location, prestige of hospital etc....
Keep in mind as well, some Hospitals do not allow DO students to rotate at their hospitals....this might piss you off as a DO student who has busted his/her butt off, to be turned away because of BS hierarchy. Nonetheless, it is part of the climate.
So in summation, unless you really value OMM, know you want primary care, and/or really love the school, or will save THAT much $$$, I wouldn't pick the DO. But if all of those do apply, it could work for you.