About the same.
Digi-coax is more rugged. and your receiver won't have to convert the signal to light to send it. But your receiver should have no trouble with the conversion. Also, optical will have no interference from other electromagnetic fields around it. Again, this really doesn't affect it enough to hear a difference IMHO.
So, either should be fine. (I went with optical cause it sounds cool to say, "I have fiber optic cables in my stereo system." Not the greatest reason, but what the heck.)