Group/user accounts management across big list of different server

Hello,

I wonder if you guys could share your experience in the above topic.
What I mean is that how do you cope with requirements like:
- create user account for new users: U1, U2, ..., Ux on servers S1, S2, ..., Sx
- create user account for new users: U1, U2, ..., Ux on servers S1, S2, ..., Sx
- give access to group of users (U100, U101, ...) on servers S100, S101, ..., Xy
- lock the following users: U200, U201, ... on the following servers S....
- give sudo access for this groups G1, G2, ... on servers S1, S100, Sx
where number of users and server can be quite long.
I am looking for solution which is going to work on both RH 5 and 6.
I know there some LDAP, AD integrated, IPA, ... solutions for this kind of tasks.

But can you compare them ?

Which of these solutions really work and doesn't involve a lot of time maintaining the software ?

Regards