when is the meeting, page-24

Boeing say there is no difference: page 10

http://www.trbav030.org/pdf2006/265_Dagget.pdf

This is because the carbon content of a hydrocarbon fuel is the determinant of the calorific value. The more carbon, the denser it is and the higher the energy. So a plane requires less volume of a denser fuel, but the same weight. I suppose theoretically conventional jet fuel should be slightly more efficient overall as it needs smaller tanks, but as the fuel is stored in the wings it makes no difference.