I saw this debate on the Naim forum a few months ago, so I tried A/B testing between Roon and the Naim app, with Qobuz as the source. I have a Naim Uniti Nova. The Roon server and Nova are wired into the same switch. I could hear no difference, although the time it takes to switch between them and locating the same parts of the track could have explained some of that perception.
Having seen this post today, I decided to be a bit more scientific. I recorded the same song from the Nova using Roon then the Naim app into separate tracks in Studio One Pro via a Focusrite audio interface, preserving the sample rate and bit depth of the original (96/24). I normalised both tracks to 0Db to remove perception differences due to loudness. Zooming in so that a single quarter note takes up the width of my screen, I could see that the waveforms are identical in every part of the song. Then using the solo/mute buttons for instant A/B comparison through DT 900 X studio headphones, I could hear no difference whatsoever. I was not aware that the tracks were being switched, it sounds like a continuous stream from one track.
Please draw your own conclusions, but I won’t be switching to the Naim app anytime soon.