These stories both feature a main character (who happens be a harem master) caught in a batlle between two sides where good and evil are not clearly defined. Both main characters enter into some extremely ecchi moments although DXD is flavored intentinoally and unsuccessfully pervy for comedic effect while Shinmai's protagonist is forced into his ecchi scenes which are more ecchi and less funny. I would say the primary difference between these two titles is that Shinmai takes itself very seriously while DXD always seems to have a tongue in cheek attitude. That being said I found myself unexpectedly entertained by both despite my initial assumptions that the story's would be non-existant.  read more
Both Male protagonists love and want to protect their sisters and will go to any lengths to do so. Both female characters want more than a brother sister relationship with the male protagonist. Both male characters are very strong and intelligent, they work best under pressure from the enemy. Both manga's share Action, magic, Fantasy, Romance, Shounen, and Supernatural genre elements.