Well, for starters, MP3 and Ogg Vorbis are both file formats like WAV or CDA (Audio CD) they're just compressed recordings of audio in the same way the a CD track is a recording of an actual performance of a song, only about 11 times more efficient (depending on the quality you choose to encode them at) than regular audio recordings.
The MT-32 and Fantom XR are the performers (if we continue the analogy). They are both synthesizers which use different technologies and have different sounds. The XR is a relatively new synth, and has (depending on who you ask :wink: ) superior sounds and effects to the MT-32, but given that the MT-32 is an 18-year-old synth, it's still quite impressive, and still sounds better than your average Sound Blaster card - In my opinion at least.
Tom has been working with the MT-32 for years and most of his recordings (MP3 and OGG) of Sierra soundtracks have been done with the MT-32 or a combination of the MT-32 and other synthesizers.
The Fantom XR is the newest addition to our little family of Sierra music lovers (Shad0wfax, welcome to the family :wink: ) and as such, we would really like to hear how Sierra games sound through it.
Up until now, it's been very impressive.
If you want to hear the difference between the various synthesizers used to record Sierra music, I suggest you try here
I hope this makes things a little more clear.