Many of our clients run multiple related programs using multiple Good Grants or Award Force accounts. Having a single user account allows switching between programs without needing to log into each account separately, and fewer account logins to keep track of.
Since users can have any combination of roles, this account switching applies to all users, not just program managers.
Similarly, as entries can be copied by a grants manager between accounts (e.g. winner of a regional program can be copied over as an entry to a separate national program account), the same entrant user account will be associated to the entries on both accounts.
Having a single account to log into multiple programs will also facilitate some planned features that will benefit you and your users in the future.