Yesterday I wrote about the GFlops/Watt performance numbers for AMD's new GPGPU and ClearSpeed showing 2-2.5 GFlops/Watt -- It looks like Clearspeed has a new card that does 4 Gigaflops/Watt at double precision.
NVidia has a new Tesla too. According to the FPGA Journal article you can buy 4 TFlops consuming only 700W or 5.7 GFLops/Watt (It's unlcear if the numbers from FPGA Journal are specs for double or single precision, but I assume single-precision). At 10 cents per kilowatt hour, a Teraflop of Teslas will cost you 153 dollars to run for a year. Not bad.
Frankly, there's too much marketing and handwaving on these specs --- not enough real numbers to make a conclusion on who dominates in efficiency.