I had a chance to listen to them both, but I was only able to demo the dx80 for about 10 minutes only due to the many bugs I encountered.
Mainly with freezes, not being able to read the memory card (64gb), not playing tracks that were selected.. Probably all initial things that could be fixed with firmware.
Sound quality was good, but not enough to make a definitive comparison. One thing I can say is that the dx80 has noticeable hiss with my Ciems, which the AK Jr has none. I also find the dx80 pretty bulky and heavy, but then again, it does a lot more. Folder navigation is much easier on the Ak Jr, though it's a bit sluggish in comparison to the dx80.
Cheers
James