[BrianG]

maxxdude, your PP ball/beach ball scenario works out for circles placed neatly on top of each other creating 4-pointed "star" spaces, but what about if they were placed in a "triangle" formation - meaning one wire in the "valley" of two others? I imagine this is how most wiring is made simply to pack more in there.

I think the only reason for more strands is simply for a more flexible wire. Larger conductors don't bend as well due to the larger cross-section: the inside edge of a bent wire has to compress and the other edge has to expand. This effect is less in more and smaller diameter conductor wire.

Another advantage, albeit small, of using smaller strands of wire instead of less but larger strands, especially for the motor wires, is the reduction of "skin effect". This is where the current in a wire at an AC frequency tends to travel along the outer edge of a conductor. More conductors means more surface. PWM is a form of AC. OK, I might be stretching and probably doesn't apply here, but I'm trying! :)