Motor whine maybe?
That Nissan thing on Top Gear last night demonstrated it, but I've never heard it on any current electric milkfloats cars
That would be my thinking, the higher the power, the torque the more intense the motor whine,
To be honest, noises are nice, but it would still be the overall package of power, drive, comfort and looks and when you see what BMW have done with the i8 then the future of performance hybrid lower down food chain does look bright.
The extended future will be solar powered cars with the roof being one thin super efficient solar panel that powers super light batteries that in turn drives high powered engines.