In our world of quest-based PvE MMOs, repeatable content is a necessity for extending longevity. If there is nothing to do, players go elsewhere. The most popular approach to this is daily (or occasionally weekly, twice weekly, etc.) quests, and that is our compare-and-contrast essay of the day. (Do not steal it for high school English class unless you define many of the terms we are taking for granted.)
More specifically, the topic is how you structure those daily quests. I call some “reliable” in that they are unvarying. The same daily quests are available every day. “Random” dailies will have a pool from which some unknown ones are pulled each day. “Rotating” is the halfway point: a pool that moves in a consistent manner, so what is available is reliably known but not constant.
World of Warcraft is the trope codifier for dailies. When I played (late WotLK), they limited you to 25/day, and everything was always available. That is one of the great merits of reliable dailies: everything is available. There is no artificial scarcity. If you want it, it is there. If you like X, X will be there for you every day. You can set up a routine, and as a developer, you want to promote having your players log in consistently. Consistency is a kind of virtue. WoW also included some randomness, like the daily fishing and cooking quests. Didn’t they extend that with the Cataclysm solo endgame, with so many of the daily quests available per day?
I find randomness good for mixing it up, breaking up routines that lead to doldrums, but it is frustrating when you want something to come up and it does not. If you are randomly picking one of four quests, there is a 53% chance that one of them will not appear in a given week. When instant gratification takes too long, this can be bad. It forces on the player what is probably a good plan (not doing the same thing every day), but players resist being forced into anything.
The Lord of the Rings Online™ is another “always everything” game. Skirmishes extended this by giving a daily bonus to a menu of instances you could pull up. That content was usually available at all times, but the quest bonus was 1/day. (I say, “was,” but I presume this continues in Isengard.)
The daily or weekly bonus seems to be the easiest approach. You can get a bonus for doing each piece of content over each time period X. The numerically equivalent but less friendly-sounding version is to have diminishing returns for repeating content.
Guild Wars goes for pure “rotating.” The wiki has a list of when everything is coming up for the 7 dailies. This contains some of the merits of the other two approaches, in that what is available is known in advance and can be planned around but is not a constant each day. Embark Beach is a Schelling point; hundreds of options would spread the players everywhere, while a small set of daily options focuses grouping. Of course, as with random, if you do not like the daily option (any of the 7?), you are out of luck, and everyone with whom you might want to group is being channeled away from you. You do not even get the hope that your choice will randomly come up tomorrow; you can see on the calendar that it will be up in mid-March, that day you will be on a business trip. Guild Wars has the additional interesting bit that you can pick up but not complete the Zaishen missions and get to them tomorrow. I am a new player still going through the campaigns, so if the mission of the day is one I expect to get to later this week, I can store that bonus.
League of Legends has a generic “first win of the day” bonus. You get it for any map, PvE or PvP. That seems to be just a “come back every day!” incentive, as it cannot channel the players anywhere, although there are few enough options that channeling seems unnecessary.
Because I have not played every MMO, the door is wide open for reader commentary on how game X did it. The hard part on doing the comparison is that daily content is usually at the level cap, and how many MMOs have you played at the level cap for any meaningful length of time? Oh wait, you read MMO blogs.
I know which site I am writing for, but please resist the urge to say, “Guild Wars 2 events will solve this” unless you can tie it back to the daily-specific focus. You know how much it pains me to have skipped City of Heroes because their repeatable content has (had?) no time limits on repeatability, although there is a task force of the week bonus.