I don't think the electric car market (in Europe anyway) has a sufficiently accurate mileage test to properly compare cars. Unless something accurate is devised, the car buyer will feel cheated.
In many parts of Europe, and all the UK, half the year you need lights and a heater while commuting, both of which will drain the battery in an EV. Okay, LED lights are better, but there is still an effect. By the time you add in a radio, music player, phone, it all mounts up.
Obviously, if you are on one of the Economy tariffs, cheap electricity over night, charging at EV at home makes sense, but only if you have a driveway or off street parking, trailing cables across the pavement is just inviting a law suit when someone trips over it.
There is unlikely to be a "Vehicle Excise Duty" (there is no such thing as Road Tax in the UK) on EVs, most likely there will be a road charging system, dearer in the commuting and school times, less during the day, very cheap at night. This should be fairer, those who use their cars the most pay the most, those with longer memories will recall that adding VED to fuel was mooted at one stage. One side effect will be that the Government knows were every vehicle is at any time, which raises issues of 'civil liberty', mind you ANPR tracks your car pretty effectively at the moment.
jh