Well, the N3 is really good. It boots up much faster than the X1-II and the UI is smooth, without the lag of the X1-II. The screen resolution is much cripser and it shows more of the album cover (still not the full square, but more than the 1/2 cover of the X1.
It scans ~5000 FLAC 16/44 and 24/96 files in about 20-25s instead of the 2m of the X1. There is NO artifacting at the beginning of tracks when you restart play ("rewind") a song. Gapless is working flawlessly. It does not have the ability to disable the auto card scan when you insert a card, which would be nice so that when you pull the card and copy a file off with no new content, it doesn't rescan. The other thing that is kinda different is that the card goes into the slot upside down (contact pads facing the front of the unit).
The AKM filters are clean and function well (the X1 doesn't have these). The extra bands on the EQ are nice, the X1 had limited bands; it made it hard to notch filter out certain peaks in some IEMs (JH-5).
The silicone case is nice, but I hate silicone cases, so a leather one in the future would be good. But, the card slot is on the side instead of the bottom like the X1. That's good, as the case covers up the card when it's on so that you don't have a chance of losing the card from hard shock.
Sound-wise, the N3 is much crisper and cleaner than the X1. The AK4490 is a richer converter and it shows. Still needs ReplayGain...
Not that the X1-II is a bad player - it's not and especially at the $99 price point. But, the firmware of the N3 is flawless (so far) and Fiio has been dragging their feet on the X1 firmware with some annoying bugs. The N3, right out of the box, is worth that extra $50!