All staff members have the same "say" in XRU decisions. We have a hidden forum here on XRU (actually multiple hidden forums) that we use to discuss issues on or about the forum. There are very few times when I have trumped the decision of the majority in the past 3+ years of the forum. I take all the staff members feedback equally.
Moderators : Can only have authority over posts/threads (editing/moving/closing/etc)
Super Moderator: All the access of Moderator + limited access to the Administrator Console for vBulletin. This means they can do things like edit user settings and access levels, modify usernames and passwords and signatures and such. SM also has very limited access to some vBulletin settings.
Administrator : Has full access to everything. All forums, all vBulletin settings and the entire Administrator console.