Here ya go, in the words of the mfg:
The X24 NC with Z chips is going to be the best of all worlds of our DACs with the AD1862 DAC chips IMO.
Then again, the Y NC does things with the AD1865 DAC chips that none of our DACs with the AD1862 chips can do...the speed and transparency are amazing…The X24 NC with Z chips sounds a bit softer, sweeter, textured, nuanced, and organic.
I am sure they both sound great although offering different presentations.