I'm searching for specs but from what I've been able to gather (without chopping up my S/PDIF cables) is that they have a 7 conductor stranded center core. Other than that they appear to be the same as your "standard" RG6 as far as the braided outter core.
They are both listed as "75 ohm coax".
UPDATE: What's the difference? Apparently the type of coax used for connecting satellite and antenna feeds are "a completely different kettle of fish". Does that explain it enough?
I keep trying to put this stuff in an electrical context so I can understand it and I think that's how this got so confused.