I'm sometimes wondering if there's sometimes some sort of DSP effect going on with the sound difference between the Coax/Toslink receivers. Computationally wise (I work in a related field) a bit is a bit, except for placebo (which shouldn't be discounted since it affects enjoyment).
Where I do work, we prefer optical cables by far, even with short runs. It completely isolates not only grounding issues, but also any wonkiness that one less-good PSU may have on another (usually sources have less refined PSU's and noisier electronics). Whether this makes a noticeable difference in a typical audio environment, and with the equipment you have (vs more hardcore industrial settings), I don't know.
Laser vs LED, polymer vs glass, shouldn't mean anything. Light still goes at light speed (the CCD/CMOS/FET sensors don't care about phase) and the only difference that polymer fibres will have is that they won't work for more than 100m or so. Then again, typical audio digital coax (without dedicated repeaters or amps) won't work for nearly that far, either. If there is signal degradation, you'll hear dropouts. It'll be obvious.
Jitter is no concern as light travels at a constant speed, as does electricity (in this sort of situation). We aren't near any black holes that I know of.
However, Coax is generally more durable than Toslink if you have items that move around at all. Glass/polymer fibres don't like repeated bending. Also, you probably have some cheapo RCA Coax cables sitting around that you can use from your old VCR or something. I promise you. In digital, a Bit is a Bit. Analogue signals... well... let's not start there :)
I only paid for an "audio quality" coax cable in my case is because I needed a custom short run RCA to BNC that wouldn't give me a rat's nest of cables (no insult to rats- the domesticated ones are so cute and smart...), and it was only 12USD :) I'd have gone with optical if I could.
Edited by Chromako - 3/31/12 at 2:29am