There are arguments in favor of both coaxial and optical, but it's difficult to make a clear care for either one being superior - optical is immune to EM and RF interference, but it does require a data conversion from electrical to optical and back. In my experience, I've never been able to conclusively find either to be better than the other. Over long runs or in an electronically harsh environment (running bundled with power or speaker cables, for example, which should be done anyway), I'd lean toward optical. Over shorter runs, it becomes more of a toss-up. If you already had a cable of one type or the other or if you had a shortage of one input type or the other, I'd say let that be the deciding factor.