Optical Cable

For the money the Wireworld product is a very good choice. Yes, there is a difference even between glass cables. I got talked into trying a Cardas cable as a loan from The Cable Company and it cost several hundred dollars. To my own astonishment I bought it as it did sound better. Perhaps not 'several hundred dollars' better, but I am glad I did it.

I just bought a Nordost Whitelight glass,very good construction.
George

Given that the transcievers are able to maximize to optical bandwidth as Nsgarch alludes to, the best sounding and extremely well-made cable IMO is a Van den Hul Optocoupler. I have used about a dozen different toslink cables, including the people's favorite (that cheap, poorly-made ebay $30.00 special). Nothing I've used is really close.

Dminches, I do no know them all. But here is a review of two of the on AA:

http://www.audioasylum.com/audio/general/messages/233584.html

Also, you can search Google for 'glass' and 'toslink'.

Since Toslink tranceivers (the little part on your equipment you plug the cable into) cost as little as four bucks, vs. ST glass optical tranceivers which cost at least $150, one determinant of whether or not you'll get better performance (than coax digital) with a good Toslink, is obviously what grade of tranceiver your component manufacturer has used in your equipment. Unfortunately, you have no control over that.

How do you know it is glass and not plastic?

What you want is a glass (not plastic) Toslink cable. But I think they're more than $60.

I have tried several different quality toslink cables but never heard a difference between any of them. The only differences noticeable were in the construction of the various cables. My top favorites for construction are the Bettercables you mentioned and Wireworld's Supernova 5. The Bettercable has one of the nicest connectors of any cable I have owned, and it fits snugly in any component with a positive locking click.