As the focal length of a lens increases the DOF decreases..I believe that stands for the most part with all formats. Switching between formats and lenses one might notice a difference, but if using the appropriate lens for a particular format things should fall into place. You have to test this with the same subject, same distance different formats, same f-stop. As always there is some interesting technical information here but again I believe understanding the basics of this is key.
Just my thought.