To me, the thing that makes Dmitry's more "Studio 54" than Rockettes is the asymmetrical off-shoulder look. None of the outfits that they studied at Radio City were asymmetrical, and I think it's because they design the costumes so that they are interesting, but also that they don't pull focus from all the smiles and the kicks. I think Dmitry's outfit (which I loved) might create a slightly disjointed visual line on stage.
You could say, well, Chris' top wasn't symmetrical either and he won -- but because it's the NY skyline, a row of Rockettes creates one long skyline! I think Chris was smarter to think in terms of it being a costume instead of a killer dress.