I haven't compared the 2, but will say, you can't go wrong with the Ruby, I love mine. I kind of wish it had xlr outputs like it's big brother the Marantz SA10, but it wasn't a deal breaker, especially at the cost.
Marantz SA-KI Ruby vs Denon DCS-A110 Anniversary Edition
I am thinking of upgrading from a Marantz CD 6007. Does anyone have experience comparing these two?