Does the rMBP run at 900/2508.
People are OC'ing to 1035/2800.
rmbp runs at 900/2500 (or 2508)--> basically the same thing.
rmbp can be overclocked to 1035 core (+135) however, gtx 660m can be overclocked to 1085 core (+135).
I don't think the extra memory bandwidth really does anything because the card does not need it.