The AWS has 24 mic pre's and is a wonderful tracking desk. its nice for mixing too.
I think someone is dishing you mis information based on what they heard and not what they experienced. However, back in the olden days before cellular telephones and when people still used these things called tape machines, i used to prefer tracking on an old neve and mixing on an SSL, though the mixes did actually do on old Neve's often sounded wonderful, and the tracking i did on SSL's wasnt half bad either.
I think the person behind the desk makes about 1000% more difference in the quality of the mix than the gear does, but dont get me wrong, gear matters to an extent. but great gear in mediocre hands will usually produce mediocre results.
Further to your question, i think a weel rounded studio should have a console that can do both tracking and mixing well. most good consoles cover that spread.
Many people move rooms between tracking and mixing because:
- it can be more expensive to rent a room with a large tracking space if you're not actually going to use it.
- some studios aim themselves more towards tracking - for example, if a room has lots of great mic pres/compressors/eqs, but not many outboard delays/reverbs etc, you might not want to mix there.
- some boards don't have automation - less necessary now maybe than previously, but many people still want it.
- some consoles have total recall, which can be important for some, especially if you're a dedicated mix engineer working for big name clients who expect tweakability.
- some people just like to be in a different space, with different monitoring etc.
As for "which console", people like SSLs for recall, dynamics section, EQ, mixbuss compressor, overall sound, flexability in routing etc. Other people like Neve consoles for the same reason (although modern Neve dynamics sections probably aren't held in the same regard as the SSL dynamics, at least not with the engineers I know).
Some are prepared to sacrifice the flexibility of recall, automation etc for the sound of a vintage console (often used as a big eq-able summing amp).