But I've got one bid from a contractor that says in NYC you've got to use plenum for everything. How do I know who's right?

Your friendly electrical inspector is the one to tell you. I suggest that you get this right because it will be a COSTLY mistake.

-Hal

CALIFORNIA PROPOSITION 65 WARNING: Some comments made by me are known to the State of California to cause irreversible brain damage and serious mental disorders leading to confinement.