User blog comment:B214/Volume 23 discussion blog/@comment-31137559-20170318011752/@comment-9595671-20170318050151

@TheUltimatePawn: I'm pretty sure Gabriel's are bigger, someone mentioned the difference between their hand abd breast sizes on animesuki, so I took a look at Gabriel's illustration and the Akeno and Rias illustration from Vol 22. Akeno's hand while held out sideways looks like three of her hand could cover her breasts vertically, while Gabriel's hand looks like it can do the same with four of her hand.

Not to mention when compared with their arms, Akeno's doesn't seem to go past her elbow area like Gabriel's appear to do. So... unless either Gabriel has incredibly small hands compared to everyone or Akeno has incredibly big hands compared to everyone, then with that I think we can all say Gabriel's successfully dethroned Akeno as DxD's bustiest known girl.