Regular Followers are more or less like Mjoll and Erandur. In addition to their basic dialogue, they offer about 50 or so revolving door comments when in your company. Some are involved in quests, many of which need to be completed prior to being eligible for recruitment.
Super Followers have commentary on quests, locations, as well as some bonus conversations for the major quest lines. How much content varies depending on the actor’s availability. Most have personal quests as well as mutual involvement in larger quests and stories.
Follower List, Stats and Locations