I’ve been keeping a tally of the Mosaic vs Roon sound quality comments that have been posted publicly as well as those that I’ve received privately. The split is a very consistent 50/50 when comparing Roon via Ethernet to Mosaic UPnP. There are also a fair number of people who hear no difference but prefer one or the other solely based on UX.
Knowing the internals of how this stuff actually works there should be no SQ difference as long as all things are kept equal. Typically an even split of observations suggests that there is no actual difference which jives with what’s actually going on under the covers.
Not trying to rain on anyone’s parade or dispute what someone is hearing, but in this case there is no actual “better.” It’s all a matter of preference so as long as you’re enjoying the whole experience and listening more then you’re on the right track.