If anything, MD-PhD would be worse, because they're much more concerned about your research, and by implication, less concerned about other positive factors you may have, like adding diversity to the class.
That said, if you really are interested in research and have a package that would be solid for a non-URM, by all means apply - URM is probably icing on the cake, especially if you can work it into explaining your motivation for research in particular in your MD-PhD statement.