To be clear about Xduoo X3 price, its 110$, not 80-90$, now, as with near every DAP lauch more than 1 year ago, it can be found for 80$, even see it at 66$ on Ebay, crazy deal for real.
Xduoo D3 is now 80, in one year, price will certainly be lower: no doubt about it.
In the 50-80$ price range there lot of choice, but near all have some drawback too, about sound or UI or construction. Fiio M3 (55-80$) is made of plastic, have no line out, good stable UI (I think) and okay sound, Zishan Z2 (40-50$) have excellent sound (AK4490 dac), but no screen and so so construction, Walnut V2S have okay sound but background hiss, no screen, but can be use as stand alone amp (27-35$), Ruizu A50 (55-80$) have BT and can play high res but I don't know about sound (don't trust Ruizu for sound quality so I will surely never try it), Hidizs AP60 (90$+) have BT, nice sound and construction and look good value but UI got problem and amping is not powerfull, there Ninthaus X10 (50-60$), Aigo DAP and other obscure chifi stuffs that surely have lot of Ui problem as well...this look a very recurent aspect with chinese DAP.
Anyway, I confirm that Xduoo D3 need to update the firmware FAST, so the UI will not ruin user experience, cause I really think it sound very very nice. I'm sincerly surprise by sound quality, not by UI because all I read was true so...I just confirm that, SLOW SLOW SLOW. About clic between track I do not heard it, it happen one or 2 times and it wasnt a noisy click, very subtle one.
So facts:
9 seconds to open.
8-13(!) seconds to begin a track from new folder.
The 2-3 seconds of begining of tracks that will not play do NOT always occur and I can't know what cause this.
For changing tracks it take about 2 sec.
DAP will play track where you stop it when you open it back(this work well).
Line out have volume control wich I like.
For such a small device, amping is very impressive from its own, about the same as X2 and X3 (250mw-32ohm, but X3 have a little more sound pressure at 112db vs 107db for d3-x2)
D3 is 2/3 the size of X3.
Sound is better and clearer than X2, and not inferior than X3, just different, some will prefer some don't, but I feel it have more body than X3 when using phone out, depending of pairing I can prefer one or another, its not like comparing DAP from another league here.D3 really is an excellent sounding DAP for soundvalue, no doubt about it.