If you mean a coaxial digital cable, not necessarily anything. They're both digital cables, but have slightly different properties. Opticals are supposed to be slightly less prone to noise generated by other electrical equipment. Coaxials tend to have a more secure fitting, which makes them more robust if you tend to move your gear around a lot. Opticals are a bit pricier too. Unless you're worried that your room is prone to a lot of extraneous noise interference, you may as well go for the coaxial. Then again, you could always compare them, either at a dealer or at home, and let us know if you notice any difference...
