The fact that BFL decided to produce their chips in a smaller manufacturing process than the competition, it's really hard they could beat their energy efficiency.
With the announcement that the bASIC was moving from 54 to 72GH/s, it was stated that more chips would be used per device. 16 chips at a lower clock and lower voltage will not only be faster, but also more power efficient. You can bet your ass their old 54GH/s design wasn't 1.4W/GHs.