Admins have ultimate control over the site. In our structure, Josh, Mi'ch, and I have the final say in promotions. Promotions are talked about in great depth.
Moderators have significantly less abilities. They cannot promote people. Much of what they can do is the functional stuff on the site: move topics, pin topics, edit posts (if necessary). Administrators have a control panel which lets them do... well, everything else. The Admin Control Panel has a ludicrous mountain of options.
So being promoted to an administrator does matter. Though if admins want to do more esoteric site things, they let me know what's up.
Hmmm. I don't know. Polarization in politics?