Aside from the motors, it's the size of the conductors and the number of parallel connections to the battery. Without getting into the physics, if you can get power from the battery to the motors faster, the car can accelerate a lot faster (and charge a lot faster). Battery size doesn't matter, strictly speaking, but a larger battery offers more parallel connections, so it matters practically. Fast launches aren't a detriment like ICE, other than the heating of the conductors. Current heats the conductors, which increases resistance, which heats things more, thus the 5 second limitation on Mach E GT. Importantly, you're not wasting electrons in the same way that you're wasting gasoline by dumping it into the cylinders. Efficiency, other than conductor losses, is the same.
It's a shame that EV's have become politicized. If you want to have fun, an EV is the best way to do it. I can't wait until my Rally arrives and I can turn in my Premium.