I understand that headroom is needed between the mixing and mastering processes. For example, after a mix is done it may sit at -6dB so the person mastering the song has headroom to play with.
I have heard that if you send a slightly-below 0dB track to a masterer they will tell you to fix it and send it back to them with more headroom. That makes sense as they need headroom to play with.
I am trying to figure out if there's any difference between mixing something to -6dB and sending it to a masterer or mixing something to slightly-below 0dB and having the masterer pull the volume fader on the track down by -6dB to compensate.
I'd think that there'd be no difference, but I feel like I'm missing something fundamental about that. So, is there a difference and if so, what is the difference?