So at a given CFM the larger fan has lower noise - ALWAYS (again - I know some bearing squeal and some have shot bearing that rattle - that is OT).
And lower RPM is lower noise. But the same RPM for a larger fan means higher CFM AND higher noise (not because of the CFM - but because at the same RPM the velocity of the tip at greater radius is higher).
With fans bigger is always better. Except when it doesn't fit. Then it isn't better.
This was the quick answer I had already, apparently to quantify and get numbers it is not so easy.
True that. However - the physics does tell you that if noise annoys you: get a bigger fan or reduce the RPM. That will be the most ROI.
If you cannot get a bigger fan or cannot reduce the RPM - only then start thinking about things such as using porous blades, blade vortex fins, etc. that will help reduce the noise.