For church websites, we use/you should use/i've seen used/i think the best is:

I think I might have posted this somewhere else, but I'll repeat it here. We're using Taxonomy Access, but that's because we're a pretty old church, with lots of established hierarchy, committees that have been in operation for 100+ years, etc. In an organization like ours, the big thing we're dealing with is fear of losing control in moving from static web pages to a CMS. Therefore, Taxonomy Access works well, because it lets everyone feel "in control" of their individual area (as defined by Taxonomy).

Organic Groups, on the other hand, would be perfect for lots of churches that are more "grassroots". In this type of organization, the roles about who does what aren't yet clearly defined. OG is a great way to actually discover what those roles are.