Which is better Coax or Optical cables

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).

For short length less than 15ft and with 24/96pcm, toslink is just as good as good coax. With toslink, There's no electrical comnection between components for those who care.  Plastic vs glass for such a short distance is silly... There's no loss of 0's and 1's with plastic.
Coax can stream beyond 24/96pcm.
Both can't do dsd.  Only coax can stream dsd converted into pcm using dop stansard (24/176.8)...
so i guess coax is better, it has less limitations.
No need to spend a fortune.  Just good shielding and 75ohms connectors.

Hands down without a doubt Coax or RCA is way better then Toslink/Optical for handling digital signals. the list in order is XLR,Coax,Optical. Toslink is last because it adds the most jitter of all. (jitter is digital distortion)

I've owned: Creative Cable Black Knight (coax), Creative Cable Green Hornet (coax), Nordost Valhalla (coax), and Audioquest Vodka (Toslink).

The only one I still own, and continue to use, is the Audioquest Vodka. The price/performance ratio, in my all digital system, is fantastic. It's got 95% of the sonic attributes of the Valhalla, just missing that last bit of air and sound staging.  

The Creative Cable products are quite nice as well, but a tad laid-back for my tastes.