I have a J3 and a D3 and I prefer the J3. I can't really differentiate between them in terms of sound.
I think it'll depend on what you want from your PMP.
For purely audio, the J3 is very hard to beat, it lasts about a week for me and takes very little time to charge.
It's also fun to change themes depending on my mood.
The D3 is a real consumer player, with wifi and most of the works.
I use it at home as right now, the firmware isn't really up to standard and keeps crashing on me.










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