Clear is more efficient in the long run, as the lumens don't drop out as fast. That is because as the lamp ages, the UV emissions reduce the most, so then the phosphor (DX coating) effectively becomes a light blocker. However, when the lamps are new, Coated can be more efficient; however the light control is worse compared to the clear equivalent, so it all depends on the application of the lamp as well as its running time/age.