The soundtrack is the original version whereas the DS version is heavily downgraded (in many ways worse than the SNES version). Given the production procedure, there could have been capacity for more ambitious arrangements, but most of the details would have been lost. The graphical ambitions of this remake really shafted the music. That said, I have few qualms with the release itself and didn't really expect much more following the Final Fantasy III Original Soundtrack.
I agree. I found this new version less focused and less effective than the original. A perfect example is the Red Wings opening. The trumpet samples in the new version are a bit more "realistic" (if you could call it that), but are weak and lack the punch and conviction of the original sounds. This kind of thing is all over the new arrangements.