Josh, optical is a digital connection, while the coax can handle either analog or digital material. There're minor differences, such as the optical connection being inherently immune from outside electrical interference, since it works with light rather than electrical signals, but the typical shielding on coax is good enough interference protection in most home environments. The coax is generally thought to be a little sturdier in its construction. There's of course no difference in the sound quality with either(assuming that any level difference resulting from a difference in the optical or coax output or input sensitivity is adjusted for). Use whatever's convenient.
