[brrt]

I don't understand what measure of efficiency you are trying to use, in which Diesel would end up being better.

In environmental discussions that measure is usually something of grams-of-CO2-equivalent emitted per km. One oddity is that the usually communicated figure is only that emittted 'at the tailpipe', which is obviously zero for full electrics. Often people try to compensate by taking the kWh-per-km figure and multiplying by the CO2-per-kWh figure for their environment. This is however still misleading if compared with the tailpipe CO2 for an ICE, because the production of gasoline or diesel are also fairly CO2-intensive.

The official term of use is well-to-wheel efficiency or emissions; there is no doubt at all that electric vehicles beat ICE vehicles easily, basically on account of the ICE being relatively inefficient because of size/performance constraints.

Obviously the actually interesting figure of merit is the lifetime emissions (and the 'useful work' gained from those emissions) and while methods and tools to compute this exist computing this in a reasonable way means making a lot of assumptions (such as the miles-per-lifetime), assumptions that will be easily attacked on internet fora, and assumptions that can easily be tweaked to show what you want to show.

The reality is that (full) electric vehicles are practical and efficient for most of the population today, if not in the very near future, and that it's hard to imagine that the current dependency on oil will last very long. Ten years is a long time.