PrgSkidmark
New Head-Fier
Ok, i find a FiiO answer in the FAQ:
http://www.fiio.me/forum.php?mod=viewthread&tid=41961&extra=page%3D1
What's the difference between Android and Pure Music mode?
In Android mode, you can install and run the third-party apps just like operating on an Android tablet. In Pure Music mode, only the FiiO Music app will be running and all operations will be limited to FiiO Music. In this way the X5 will work as a stable and pure music player
So I deduce that there is no difference in audio quality level, so I do not really worry about losing the "pure audio" in exchange for opening a bit the Android ecosystem
I was listening to Celine Dion and found in Android mode the vocals had a divide in the middle of my face with her voice on each side, and in pure music mode that divide was gone and her voice was in front of me. I don't understand why but the Onkyo app sounds like FiiO music app in pure music mode. The FiiO music app in Android mode sounds different than the Onkyo app.