Bobby Roberts
Banned
I can't honestly think of the last time I used Coax to connect surround sound. Maybe my LD player? More often than not, a device will have optical over Coax for that connection. Optical is way more common in devices and I bet in practice. I'd really be surprised if this is true at all.
Most devices since 1996 offer both right next to each other - including Laserdisc players. Since RCA cables are ever omnipresent (and you pretty much have to go out of your way to purchase a TOSlink cable, often at inflated prices) people, in my experience, choose to pass digital signals via the coax option over the TOSlink.
In fact, I'm pretty sure a fair amount of Blu-Ray players bypass the optical option entirely, only allowing for analog stereo and coax digital as audio options aside from HDMI. The number of devices that are optical only as opposed to optical/coax or coax only is probably in the minority.
We're both just kinda guessing here, though. It'd probably take some google-fu to figure this definitively.