Well, I'm just talking about perceived size, essentially. I just believe that the DS2 should appear to be more massive next to everything else in the film. For example, at the end of ESB, you see the size of the Falcon and TIE Fighters next to the Executor, and they look like insects in comparison to it. The Super Star Destroyer is obscenely gigantic next to these little ships, and you finally get that relative scale. You don't get that with the Death Star II because all we really see it properly in scale to is the Endor moon, and it doesn't look that large.

-NJM