I have both Noteburner iTunes DRM Audio Converter and TuneFab Apple Music Converter. Both of them can convert Apple Music tracks and audiobooks to MP3/M4A as advertised. Personally I think TuneFab is better than NoteBurner. I have listed feature difference as below.
1. TuneFab can extract audio from any videos in iTunes, including purchased movies, tv shows and home videos while Noteburner can't.
2. TuneFab allows users to rename and organize output file names and folder structure using ID3 tags like artist, name, album, etc. while Noteburner will use same name and structure as Apple Music songs. TuneFab will be more inconvenient when you want to rename the music using format "artist - title.mp3" instead of "01 title.mp3".
3. TuneFab allows users to edit metadata while Noteburner can't.
4. TuneFab supports more audio output formats.
As to interface, NoteBurner supports multilingual interface while TuneFab only supports English.
TuneFab is kind of old-fashioned while Noteburner comes with a modern interface, however, TuneFab integrates iTunes playlist in UI, which is more intuitive for beginners.
As to conversion speed, TuneFab claims 16X faster while Noteburner claims 20X faster. In my test, they cost almost same time to convert a playlist of 15 songs.
Overall, I think TuneFab Apple Music Converter is a better choice.