Imo, purely base on sound, M2 is similar to the Fiio x3 (I still own) or x3ii (I sold) range. With this current lmue promotions, this is a very seriously tempting buy. Anyone looking for a good dap (less than USD$200) should consider this.
M3, is in a total different league. To my ears (and synergy to my iems), I can be very happy with M3 (I own it, like the sound, but not the size and weight).
M2 has the portability and the form factor, but unfortunately, the sound (I used FAD IV and GR07B during my audition) just did not entice me (I did tried very hard to like it).
Based on reviews, some said M2 is a 'neutral', 'bright' dap, etc (and with compatibility issues using multi BAs due to its 7ohm output impedance?).
I think that was what I heard. Unfortunately, I prefer a warmer, organic sounding signature (nothing still beat my shozy alien).
And so, I can't just bring myself to buy the M2, even though it is now heavily discounted...just too bad.
For others, you should seriously consider the Shanling current sales price, grab it before the offers end.