The problem with mp3 is that to make the file smaller, the encoder has to take something away from the music (The smaller the file the more gets taken away) which can never be got back. (It is gone forever)

If you record in a lossless format (Such as FLAC or uncompressed WAV) every part of the music is retained, and thus is ideal for storage as the Master.

If you wish to convert to another format, then by converting from a lossless file you can be sure you are getting the best possible conversion you can get. (Something that cannot be achieved with a compressed (mp3 for example) file)

It is always best to record to a lossless format and then convert to a smaller file if needed. (Not the other way round)

Bill