neither. there is no difference. they both carry digital signals and as long as you have a good quality version of each their performance should be identical.
which one is more practical for your application is a different question. It depends on your DVD player, Receiver, etc. My DVD player only has Coaxial. My CD player only has Optical. My receiver has a limited number of inputs for each, so my equipment dictates my needs.
Longevity is another issue. You have to be more careful with optical. You can't bend it nearly as much or you could damage the fiberoptic wire. Also, it is more difficult to find long runs of optical cable, whereas long coax's are more readily available.