It all depends on your goals. For bodybuilding purposes, conventional deads recruit more muscles, which I think would be ideal for a BB. In powerlifting, I think it is a good idea to try them both and then train the weaker one, and pull the one you are most comfortable with in competition. For athletes, I like conventional because it recruits more muscle. However, for speed work, I like sumo because it is a short, explosive little pull.