"My guess it's because DD 5.1 is compressed"
That would be my guess as well.
And, as to the prices of the two, I'm betting that the Dual Discs are being subsidised right now by the record companies, and that is why they are cheaper than SACD/DVD-A.


Axioms; For when you've just Gotta have More Cowbell! 60s 150 350 8s 2is RX-V2500 DVD-C750 2900