Jcc3 -- I believe that w/ your Krell stuff, you're talking about AT&T ST glass fiber optical connectors, and not Toslink. And to clarify the electrical thing, it's not so much about carrying a charge but rather that fiber optic ICs (Toslink OR AT&T) are not conductive and therefore the equipment is electrically isolated from each other -- sometimes an advantage when hum problems arise.
As for the glass (AT&T) vs. coax or AES/EBU issue, it really depends on the quality of the cable in both cases. If you are talking about premium examples of either kind, for instance, Aural Symphonics Optimism 2 AT&T glass fiber ($1000) vs. Purist Dominus or Siltech coax or EBU (>$2500), I would have to say go with the glass (AT&T, not Toslink) if your components have AT&T inputs/outputs.
In a choice between Toslink and coax, I'd say go with the coax if it's reasonably high quality (in the $200+ range.) If it's just junk coax, you probably won't hear any difference between the two.