If you compare Tidal playing on M11 and N6ii, I would pick N6ii, no question.
I actually don't like to talk in absolute terms because our gear, taste, music, etc are so diverse. So I'll list the basis of my preference here, for your reference:
What I didn't like of M11
- Most of my IEMs have impedance less than 15ohms (minimum recommended by FiiO) -> constant hiss
- Even with higher impedance full size headphones, noise floor was too high
- Overall too flat and lacked body and depth
- Imaging was strange - Too much Left/Right separation or lack of crossfeed
- Had a lot of problem with USB DAC with digital noise
- Audio lag watching videos
- Player software was half baked
What I got with N6ii
- Works much better with low impedance IEMs. I can use Andromeda out of SE most of the time without IEMatch.
- Much fuller sound, lower noise, dynamic, warmer, spherical sound stage
- Choice of A01/T01/E01/E02!
- Serves well as a portable, desktop source via SPDIF, and USB DAC (haven't tried I2S yet)
- Software is stable and works as expected
If you had similar issues with M11, there's a chance you will like N6ii
![Headphone Smile :) :)](https://cdn.head-fi.org/e/headfi/smily_headphones1.gif)
Happy hunting and listening!