The obvious question here is why is memory source playback perceived to be better?
The only justifiable claims that immediately come to mind are:
- System/network is of too poor performance to manage uninterrupted playback when storage access occurs. Unlikely these days when even a raspberry pi can manage this.
- DAC is excessively sensitive to noise induced due to digital activity in the host computer - sounds like a badly designed and/or ancient DAC.
Most music is produced (mixed and mastered) using just in time playback from fast local discs in the DAW and monitored on highly revealing sound systems by people who are often highly attuned to the slightest quirk or glitch.