M4A is refused by some car stereos, older players, editors and upload forms. TTA stores audio losslessly in a smaller file than WAV. M4A is at home in music and voice memos on Apple devices; TTA is the usual choice for archiving CDs without losing quality. TTA cannot bring back detail that M4A compression already removed; it simply stores the result without further loss, in a larger file.
The defaults suit most files. Under Options you can trim the start and end.
This pair uses the compatibility engine, ffmpeg built for the browser, because TTA cannot be written by the browser's built-in codecs. It is a one-off download of about 10 MB that the browser keeps, it is slower than the built-in codecs, and it takes files up to 1 GB.