Optic has avantage of No EMC interferance
What is EMC, did you just make it up?
RCA Analog are 50 Ohm and thay make a diffrence in high end.
RCA is the name of a manufacturer. Cinch connectors, (what everyone calls RCA connectors) are neither 50 Ohm or 75 Ohm.
There is no need for an audio cable to have a characteristic imedance of 50 or 75 Ohms, because there is no impedance matching taking place.
The only commonly available 50 Ohm coax cable is RG58...and it's generally not used in consumer audio applications.
nah, it just adds more material to the myths that a lot of you subscribe to.