Nightf0xxI don't have the N3 so I can't compare. You can check out my Head-Fi review of the X1 II at http://www.head-fi.org/products/fiio-x1-ii-high-resolution-lossless-music-player-2nd-generation-silver/reviews/18098.
Looking purely at the specs the N3 has a better DAC though the SNR and other specs seem to be a tad lower than the X1 II. However if you are using IEMs and other low-powered devices the difference should not be large, it's more obvious if you are using power hungry large headphones. I know it's not possible but DAPs are best auditioned. As you will see from my review I was happy with the neutrality of AKM DACs but just found it a bit lifeless on my daily commute.