digital optical interlink vs. coaxial

The digital information travels through the cable or optical fiber with essentially no error. Problems can arise as follows:

Coax is susceptable to pickup of electrical noise, that may affect ability of the receiver to distinguish "ones" from "zeros".

Inferior wire and/or improper receiver impedance can cause distortion of the digital pulse shape, again affecting recognition of one's and zeros.

Both coax and optical drivers and receivers can be designed and built well or badly, again with the possibility of data error.

Optical transmission gives complete electrical isolation. In the case of audio circuits this may avoid hum problems. ("Optoisolators, which are just optical links about one millimeter long, were in general use for this reason before fiber optic communication links).

An interesting thing about fiber optic communication is that duplex communication (both directions) can be done simultaneously through the same fiber. (The photons you send to me don't interfere with the photons I am sending to you). Can't do that with wire.

For a "long" run (I would guess that would be more than 20 feet or so) I would prefer optical. For shorter runs there should be no difference (with good equipment).

Cytocycle...Please explain what you mean by "bandwidth" of an optical data transmission media. The light source is monochromatic, so any deficiency of "bandwidth" would just amount to lower transmissibility. The optical light source circuitry and the light receiver may have data bandwidth limitations, but that has nothing to do with the nature of the fiber.