Optical cables

Is there really any difference between them? I notice PMMA (polymrthylmethacrylate) ones are touted as best but surely there can be no difference with optical?

I'm comparing CAMBRIDGE AUDIO DIG300 which is PMMA and the IXOS XHD308 made from medical grade fibre optic cable, both are £20 at Richer.

Thanks

 

My experience is that different types will give the same performance if kept short - so up to 2 meters or so and any type should be fine.
When using long cable over 3 meters I've evidenced some variability and certainly with 5m+ you'll get some that are a lot better than others.