I seem to be the odd one out and prefer AT&T optical. But, only if you use a very good optical cable - most of the industrial types sound awful, and the guage of the fibre needs to be right, and you need to use suitable termination aids like the Theta gel-like stuff. A very good optical cable will sound cleaner, more detailed and more dynamic than very good coax, but the clincher for me is that coax always (at least for me) adds an artificial warmth due to earth noise. To validate the last comment - I hear this earth noise even if I listen to the AT&T connection, when the coax cable is left in place - but the earth noise is removed when the coax is removed. I can well imagine that for some, the added warmth of the coax is preferred - but since it is actually noise, then I suggest the problem should be fixed elsewhere.
