Other factors when considering electric propulsion are instant availability, simple controls, lack of altitude effects, no icing or fuel contamination issues, very accurate range/endurance information and superior reliability. Also, not being surrounded by large amounts of flammable liquid in an accident is a bonus.
At the moment, as pointed out in this thread, battery tech. hasn't advanced to the stage where it is close to fuel in terms of energy density but the form factor is much better, i.e. you can put batteries anywhere, like the wings, whereas an engine is a big lump with aerodynamic and/or balance problems, wherever you put it.