3 reasons why Tidal can sound different from local storage:
1) Local files are different from the ones Tidal have (different masters used).
2) Software difference (MPD vs Tidal through RAAT vs. Tidal native (not sure about the last)). With RAAT, there's constant network traffic on my BDP-1. I don't know if its better on the BDP-3 though with the larger memory. It'd be nice to preload the entire track in advance. Right now, if I unplug the ethernet cable on the BDP-1, the music stops very quickly. The buffer needs to be much bigger.
3) Hardware and noise differences due to accessories used (ethernet vs USB (flash, SSD, spinning)) and their power supplies.