Mixerboy wrote
make the mp3 1db louder and unanimously it was chosen as sounding "better"
That's true of any comparison though.
I'm with Sharon on this one. Mp3 is too much of a compromise - there is a huge difference to the sound quality, frequency balance, etc. - even using Lame at 320kbs CBS. Fine for a final downloadable version (which IMO should be mastered differently anyway), but to take a compressed mp3, work on it with plugins (which probably have a 64 bit internal signal path) and then pass it through a lossy compression algorithm
again to send it back is a bit too much of a compromise -
especially for critical listening, and won't do the mastering engineer's abilities any favours at all.