Quick survey, before @fentonsteve comes along with the physics of signal transfer – and the answer!

All other things being equal: and considering a CD transport with both optical and coaxial outputs, into a decent DAC with both optical and coaxial inputs; and good quality optical and coaxial cables of the same (short) length; which will give the best sound, theoretically (ie, I know you’re supposed to use your ears to decide)?

Thanks.