Which is better Coax or Optical cables

You have to pick the distortion that sounds best to you.

many of these replies should be used in a college electronics course on why consumers buy snake oil

if you have an opinion then state why you think one is better than the other

that will make for a suppirier thread

Plastic fiber TOSLink cables -- basically everything available on Amazon -- are junk. Cheap plastic cables can barely handle the bandwidth required for 44.1/16 (for the most part not even that) forget about anything higher. 

The problem stems from losses due to internal reflections. You need very fine, high-purity quartz-class conductor bundles and polished connectors to reduce reflection losses to to negligible level. Of course the quality of the receiver and transmitters play into this.

There are also high grade plastic cables out there such as the mid-level AQ and Supra cables that are supposedly the sweet spot for price-performance. I haven't compared any glass cables, but I do have a Supra cable that cost around $80, and have confirmed it competes in SQ with a filtered/isolated USB connection running off my dedicated audio PC. 

Check the spec's on toslink vs coax connections.  Toslink is limited to 96khz plus it's construction is generally inferior to coax, certainly when compared to a really well designed coax.  I use an MIT Magnum Digital Coax which produces superior sound to my previous $12k balanced cable running analog from my Krell Cipher (which I now sold).