Adam, from a design perspective, is an electric motor of a given HP rating smaller than a hydrocarbon motor of similar HP rating?
(The ratio of power and/or capacity to weight is another major design factor, is it not?)
If I get electric drive, but add more weight to get it, what have I gained?
I find this line of progress analogous to the environmental constraints on using various chemicals for industrial processes. The processes become, in some cases, more expensive or more time consuming. The benefit from that cost being "less poison" and therefore less cost to clean up. Chemists keep on working to mitigate those constraints.
The breakthrough in fuel and power technology to replace hydrocarbons for this particular application (aviatoin) has yet to be found. Don't mean to rain on the parade, but I don't think electricity is the golden bullet in this battle.