You think so? Michael might be the better fighter, but he's also too straightforward in his thinking. Bel would probably take his presence into account and pull something unexpected that'd just leave them both confused ... or wait until Michael was otherwise ocupied. Raphael managed to surprise sweet low ranking Crowley once, but by now most people in the manor are probably warned and Belial's survived in hell for thousands of years. Not to mention that he's the archangel's own level.