Why stop at base-20 when base-1000 is available? https://en.wikipedia.org/wiki/Cistercian_numerals
As it happens, we've learned to make two-state devices way more cheaply than three-state devices, so binary wins in the real world, but if we figured out how to make three-state devices for at most 1.5 times the cost of two-state devices, base three would win.
It's fun to prove that base e and base 3 are theoretically more efficient than base 2 (and not all that difficult...only basic calculus is necessary).
Only in one dimension.