[kaefert]

who has the best decoder in these devices that is significantly better than the other in terms of sound quality ?
The Pi or the Receiver ?

hahaha that's meant as a joke, or are you really asking that question?

Surely by definition of them being lossless codecs, if it's decoded the resulting output is lossless isn't it?

I don't think / believe that DTS-HD MA signals can be decoded into PCM signals without any loss.