Mostly i'm using foobar2000 to do the tagging job and i start mp3tag when i need to do some exporting and other stuff fb2k is not capable to do.
I use the "UNSYNCED LYRICS" field to store the lyrics and the "PUBLISHER" field for the record label name. The same fields are used for all formats.
However if i open the files i tagged in foobar with mp3tag the field names are different:
on mp3 files "UNSYNCED LYRICS" became "UNSYNCEDLYRICS, on flac files it's the same (with the space)
on flac files "PUBLISHER" is "ORGANIZATION" (on mp3 files it is still "PUBLISHER").
These are just two cases i noticed, it is possible that there are several more.
This discrepancy makes exporting a lot more difficult, because i need to use different script for MP3 and FLAC files (or create a "universal" one, but i'm not as good ).
I can't rule out that this is a bug in foobar, but it would be good to have these two excellent programs compatible....