In theory, optical is better as there can be no chance of ground loops. Ground loops CAN manifest in the digital and analog domains.
In the first, it can produce significantly more jitter, and was for a time a significant source of issues with PC/laptop based systems when powered from the AC. Batter power and better isolation seem to have taken care of most of this, same for USB.
There has been some claims that the receivers just tend to be better for coaxial, but also conflicting claims that coaxial receivers are often not optimized for S/PDIF.
In any event, I use USB for it all now. Sounds good, and much higher bandwidth.
In the first, it can produce significantly more jitter, and was for a time a significant source of issues with PC/laptop based systems when powered from the AC. Batter power and better isolation seem to have taken care of most of this, same for USB.
There has been some claims that the receivers just tend to be better for coaxial, but also conflicting claims that coaxial receivers are often not optimized for S/PDIF.
In any event, I use USB for it all now. Sounds good, and much higher bandwidth.