Honestly, I can't say which I prefer, and that's mostly because I generally don't enjoy MMO stories at all. For what they have to accomplish and what they're working with, MMO writers (and game writers in general) do a great job, but there's just too much working against them to truly write something exceptional. Suffice it to say that the well being of the game trumps the story in 99% of cases and because of it, the narrative will never be great. One can write a wonderful 'chosen one' arc just like one can write a 'random person' arc in any other medium. Either way, both will wind up being not very good or engaging when saddled with a game. In my opinion, of course.
