From ordinary RCA cables, the digital coaxial cable differ in that the inner usually no braid, but a single-core copper cable is used with a resistance of 75 ohms and the cables are better shielded usually similar to modern satellite cables. The exact technical structure, each Googling yourself or look at Wikipedia.
Of course, there are differences in quality and workmanship of the plug, but that does not matter for the purpose of the home theater system. The signal arrives.
Those who invest a lot of money in his home theater should not save in the wrong place and invest the few euros in a neatly shielded cable with defined resistance here. Cable as they exist at the avarice markets, although cost more, but that's all. The signal quality is no distinction can be established!
Addendum of 09/09/2014:
The cable still works flawlessly!