Not to mention, QA, is that the former two don't force complete urgency down upon you, as the latter, OB, does.
DF: Took about a decade in canon. So in that time, you played the political game and did things to keep food on your table. To everyone, you were some regular guy. To the royalty, you were a pawn for them to play with.
MW: Shorter canon-wise, but your commander would tell you to occasionally do some of the MQ and keep your profile clear by adventuring, climbing the guilds and factions, and things other than MQ. It was pretty much "okay, I need this book. *days later* Thanks for the book, here's some money. Now buy yourself some nice things, and keep your cover; it'll be a while before before I digest all this information." You were an undercover agent, who job didn't require them to do everything immediately.
OB: ZOMG! GET THE AMULET, SAVE THE WORLD, MADMAN ON THE LOOSE AAAAAAAAAAAAHHH!!! You had to save the world, or else everyone dies. No room for fun time, daedra were knocking on the city gates.
I would actually consider myself a Sentinel Champion for all the stuff I did for them, though I did not give them the Totem.
There was no real urgency in Oblivion, even though Tamriel was experiencing a daedra apocalypse, the daedra would just sit around their gates and not really do anything. Although it would be awful if the game suddenly ended if you took too long.
I dunno, people are always talking that the world is coming to an end, portal are popup everywhere (despite the fact the foe just stand next to it but will attack anything they do not like), provinces been reported for being attack, not to mention Kvatch been besiege and ruin. The urgency is there, but all in a sad "pause" and cannot go further unless PC does something.