These days I really think that as in ANY classic sense of record making, it depends on the project and it depends on the engineer. I was working on REALLY great R&B record the other day, ala "Song in the key of life", in which each session had no less than 160 track and the producer/engineer had been working on the record for a series of years. In this case do I think the producer should do it? No absolutely not. He had tracked a number of tracks to leave himself an out. He and a set of outside ears needs to make decisions based the tracks from the perspective of someone who had seen the project from start to conclusion or otherwise as a total project-overseer and as an astute listener(hired mixer). Again, as it has been forever, what are you good at? What does the project dictate?