okay, so the keyword here is >format. you say they use different formats, but you purposefully (and understandably since you don't know) omitted what they specifically are. here's a quick recap.

NSMBDS, like most DS music and like the majority of old games on systems with limited storage space and/or audio capabilities, uses sequenced music as a medium to produce full tracks. sequenced music is saved into the game as sheet music (MIDI-type files) and fetches instruments saved separately and individually as a library, ready to use for the song it's intended for.

the SSEQ format NSMB uses is very close to MIDI format and can thus be converted back and forth, losing only minor-ish information.
both the music sheets and the instruments can be exported and converted into useable formats, but encoding new tracks into the game requires some manual effort to make it work well.

streamed music on the other hand, is more like ready-made audio files that take much more space; but can allow a much bigger variety of filters that cannot be achieved with sequenced instruments. imagine you pick up a song from the internet, it's most likely gonna be a single file like a MP3 or whatever. that's a full, standalone file.

streamed encoding became a mainstream for newer games that don't have major storage concerns. these tracks are an advantadge not only for what you can put into them, but also because they are much harder to steal if you're looking to remaster them; since there is no way to access the music sheet without manually recreating it, through your own effort.

and of course they're much easier to deal with, contrary to having to code a system to fetch sequenced instruments; which is both of a hassle and a now unnecessary practice due to technological advances.


that was longer than expected, I hope you get the gist of it.