"Pretty much impervious to noise induction anyway"

Ever heard of Jitter or Bit Error Rate (BER)? Digital signals aren't impervious to noise, its just that you may not notice because the error detection/correction algorithms will tend to filter it out.

From what I've learned about the two standards, the coaxial link uses a significantly higher carrier frequency than the optical link, so theoretically at least it should provide a "better" signal. In practice, I think you'd be hard pressed to notice any difference even with high end audiophile gear.

Graham