Mac: create group for use with mobile & local accounts

Question

I need to create a group that will contain the local admin of a machine and one or more Network (Mobile account) users (from a Mountain Lion Server).

I'm wondering where to create the group brewers (for homebrew. I need a few users to be able to brew but I don't want to add the network users to the already existing admin group).

I could create the group:

• in the Users & Group System Preference or…
• in Server.app on the server.

Is there a preference? Is there a functional difference? The group will have users from both a local account and the networked account.