I just checked the Friction Facts report from 2013 and the difference between the most efficient and least efficient set of pulleys is 1.337 watts.
The least efficient were Shimano Acera pulleys at 1.37 watts. The CeraminSpeed Gr3 pulleys were 0.033 watts. The worse ceramic pulleys were the FSA Ceramic at 0.285 watts.
For comparison, Shimano DA used 0.181 watts. SRAM Force/Rival at 0.146 watts. Shimano Ultegra 0.607 watts.
The average difference between ceramic and steel bearings was trivial. The steel used 0.013 more watts.
Sleeve bushing pulleys were the worse at an average of 0.577 watts.
Home page Friction Facts