Best Practises for using Content Types

Question

We had third party vendor who migrated and re structured contents and sites in Sharepoint 2010. I noticed one unusual thing : In most cases they new separate site content types for every library in a site i.e. even if two libraries contain same set of metadata
columns they created separate site content types by duplicating it from the first one and gave it unique name and used in second library.
My point of view for content type is that they are used for re usability, i.e. if another library is needing same set of metadata columns then I would just reuse existing content type rather than creating another content type with different name by inheriting
it from the first one and having same set of columns.
When I asked vendor reason for this approach (for every library they created new content types and for libraries needing same set of meta data columns they just inherited from a custom site content type and created another duplicate one with same set of
meta data columns and gave it different name in most cases name of library ) they said they did that to classify documents which I did not agree with because by creating two document libraries classification is already done.
I need some expert advice on this, I will really appreciate: I understand content types are useful and they provide re usability but,
 A) Do we need to create new site content types whenever we create new library ? (Even though we are not going to re use them)
B) What is best practice : if few libraries are needing same set of metadata columns
1) Create site a content type and reuse it in those libraries ? or
2) Create a site content type and create new content types by inheriting from site content type created at first and just give them different name even though all of them are having same set of columns  ?
I need expert advice on this but following is my own opinion on this
I do not think point A) is a good practice and should not be used, we should create site content type only when we think it will be re used and we do not need to create site content type every time we create document library. Also I do not think point 2)
of B is a good practice as well
Dhaval Raval

Answer 1

It depends on the nature of the content types and the libraries. If the document types really are shared between document libraries then use the same ones. If the content types are distinct and non overlapping items that have different processes, rules or
uses then breaking them out into a separate content type is the way forward.
As an example for sharing content types: Teams A and B have different document libraries. Both fill in purchase orders, although they work on different projects. In this case they use the same form and sharing a content type is the no question approach.
As an example for different content types: A company has two arms, a consultancy where they send people out to client sites and a manufacturing team who build hardware. Both need to fill in timesheets but whilst the metadata fields on both are the same the
forms are different and/or are processed in a different manner.
You can make a case either way, i prefer to keep the content types simple and only expand out when there's a proven need and a user base with experience with them. It means that if you wanted to subdivide later you'd have more of a headache but that's a
risk I generally think works out.