I do not think it really matters. They are only containers with materials. Looking at my just installed 2021 I only see the AEC library.
What can be interesting is which materials to use

You can see some materials have a small triangle with an exlamation mark. These are the older Autodesk materials. The ones without that mark are newer materials and are PBR Materials (Physically Based Render).
PBR materials should be more physically accurate. PBR materials are widely used in all kinds of render engines and other software (e.g game engines like Unity, Unreal). So you could expect better qaulity renders and better export to software like 3ds max. I expect that the older Autodesk materials will slowly be phased out in the coming years and everythng changed to the PBR materials..
Louis

Please mention Revit version, especially when uploading Revit files.