From what I've seen I think they're very similar.I had one from Japan, bought on ebay without problems. It was simply perfect.
In fact, I'm planing on buying another one.
Also MUSYNC just got an update of, if I'm not mistaken, 3 more songs. (For a total of 12)
Edit: Top of the page. Buy Cytus Lambda, MUSYNC, DJMax Technika Tune, DJMax Portable 3 and the new Pinball Arcade tables when they come out.
I think I must have counted Kerb Eros which is an old song(?).Just 2 songs for now, but it seems the "Coming Soon" screen is reserved for previewing another song coming even later.
Also, thanks for the writeups on this. I have no DJMAX Portable games (Technika is more than enough right now), but decided to jump on board with this at the ground floor instead.
The first new song, 'EV.OTE ^IOV.OIA' (Or you know, however it's spelt) is a really fun playful classical piece and 'Tales of Ginkgo' is evocative of the soundtrack to an anime.