OpenDAW is different beast in the same field. It's a full music editor and suite, where you can write notes down on a piano roll (or record with midi), then use synthesizers and samples to turn that into a song.

Audiomass is an audio editor, meaning that it works with already existing files that might need to be cut, edited, cleaned, or filtered, or in case where one has multiple stems put together to be mixed.

Think of it a bit like vector vs pixel editing. OpenDAW is vectors (music info), audiomass is pixels (music data)