Electricity does in fact move at less than the speed of light in coax cables - something like 75-80% of the speed of light. This specification (propogation delay) is found in the spec sheets of coax cables.

Audibly, this doesn't matter squat, unless you take into consideration the micro-nano-fly-fart length of time you are having to wait to hear the music verses from an optical cable. On the other hand, the processing needed to change the electrical signal to light and back again at the ends of the optical cable will introduce their own delays.

Which delay is greater? Does it matter? Do you care? Do I care? Does it effect the price of tea in China?

I don't know.......