I'm confused... MiniDisc (at least back when I was really into them) used ATRAC encoding and not MP3. Also, any input (be it 48khz from DAT or 32khz from DSS) was converted to 44.1khz to be put on the MiniDisc.

As far as I know, all MiniDiscs are 44.1khz, 16bit. You can get high end decks that have 24 or 32 bit processing (I think - probably in the DAC) but that doesn't effect the files on the disc.

Minidisc was never touted as being superior to CD's. Only more convienient. Becuase of their encased platers, there is little risk of getting the surface dirty or scratched. And they are so small. Minidisc is a "lossy" compression, so it's audio could never exceed that of it's source. It was meant to "compliment" CD's and replace the audio casssette.