I usually save files as WAV files and rely upon the file name (track name and number) and directory (type e.g. classical or rock, sub directory artist, sub directory for albums) for the information. Speech and drama I usually recorded as MP3 at 320 or 192.
For use on portable devices I have a duplicate set of all the files converted to AAC by iTunes at 128kbit/s
iTunes truncates the information in the tags, particularly the comments where I might have a screen full of text and the file names of the WAV files with artist, album and track gets cut down to a bit of the artist's name and only sometimes the album title.
I then have to track down these 'errors' and cut and paste from the MP3 (filename and tags) to the M4A (AAC) file to add the full text.
There might be another program that converts and retain the original MP3 filename and tags - but it could be hard to unpick (unselect) the ones that are correct having been imported twice - once as a WAV sans metadata and secondly as AAC with metadata.