User blog comment:B214/Shin DxD 1 discussion/@comment-2601:340:C501:C683:D9E9:7B80:4551:9FCA-20181113211020/@comment-1359322-20181118163658

^There's a major difference though. Lets say if Ise didn't marry Rias. If Ise lets go of his Maou post he would become a Hyoudou again. Rias on the other hand, even if she lets go of her post as Gremory Head, is still a Gremory. Hyoudou vs Gremory, it's obvious that Gremory > Hyoudou. Either way it doesn't matter much since Ise will marry into the Gremory family.