A gallon of gasoline contains ~114,000 BTUs of energy, while a gallon of ethanol contains ~76,000. Therefore, under typical conditions, operating with an ethanol blend will result in reduced fuel economy. How much depends on the blend, the driver, the vehicle, etc.
Regarding power, adding ethanol to gasoline typically raises the octane (see the 100+ octane of E85 as an example). The higher the octane number, the more resistant the fuel is to detonation (knocking). Higher compression ratios can increase power, but increase the risk of detonation. This is why performance vehicles often recommend the use of high performance fuel. If the engine is designed with high compression in mind, ethanol-blended fuels may increase performance if the octane rating is higher than comparable "straight" gasoline.
Ethanol can be harmful to fuel system components not designed for it, especially in higher concentrations.
Some engines simply "don't like" ethanol blended fuels. My 2001 Honda, for example, gets roughly 10-15% worse fuel economy with E10, regardless of octane, compared to straight 87 octane gasoline.
Run five to ten tankfuls of E0 and E10 through your vehicles and keep detailed records of price paid and observed fuel economy. Then decide if ethanol "makes cents" for you.
I doubt you will find "truth" about the economics and politics behind ethanol as all sides of that controversy will be biased. Numbers can lie, especially if it is a lie by omission.