Please quantify this. I also have both - and the answer is ..... it depends on.
- Which module the Q5 has, and what headphone you're using
- Your personal taste in tonality
- How you want to listen to your music
- What you value in portability
For example - and these are the first ones I thought of.
- if I prefer to have a more minimal and more portable experience, I might find the X5iii or the M9 better than a Q5 - as then I don't have to carry a source device as well.
- if I prefer to have my phone decoupled from my music - then the choice is obvious and its not the Q5
- If I'm listening to IEMs and don't need the extra power, then it becomes a real choice (preference of tonality)
In terms of sound quality
- Both have distortion levels below our audibility thresholds
- Both have low impedance outputs
- Both have good SNR ratios and cross-talk measurements beyond our audibility
Saying one is better than the other is (IMO) quite silly. The answer is - it depends on what your preferences are. SQ is about the same.
The better answer is:
- If you're driving a harder to drive headphone the Q5 has better power options - depending on the module
- If you prefer a warmer, richer tonality, both can be viable options - but with the Q5, you will need a different amp module to achieve this
- If you prefer a more neutral sound, the Q5 has better module options to achieve this
- If you prefer a device to uncouple yourself from your phone - then the X5iii or M9 are better options
- If you prefer your phone's UI and just want better SQ than your phone, the Q5 is probably the better option
I could go on - but you get the gist. Saying the Q5 is "much better" than the X5iii for Spotify listening - without quantifying context is at best misleading, and at worst totally incorrect. At least find out what the person values (attributes), then you can give them a more informed reply.
FWIW, I use Spotify, and have both the Q5 and the X5iii. They are both fantastic sounding devices. Unless I'm using the HD800S, Alara or HD300, 9/10 I'll either be using the X5iii or direct from my iPhone SE. If I'm using my full sized, and moving around the house - then I'd take the Q5.