I like games that encourage exploration of the worlds they are set in. Whenever I play a game for the first time, I usually take breaks throughout the mandatory plot just to wander around, take in the scenery, the atmosphere, and admire the little details the game designers sprinkled all over the setting.
I know of a part in Skyward Sword, where you are in the Faron Woods and have to chase some weird bulbasaur/penguin hybrid. During that scene, if you try to stray from the path, the game will not let you do that. Fi will interrupt your play, talk to you about how your dousing readings point into a different direction, and she will actively block your path.
For the explanation aspect of gameplay, this is somewhat of a fatal blow. Older Zelda titles, especially Ocarina of Time, Majora's Mask, have always encouraged exploration. I can think of no situation in which either Navi or Tatl have ever actively prohibited you from going somewhere. It is the job of an exposition fairy to subtly guide you and teach you about the mechanics of a game. If an exposition fairy exceeds that role, and insists on confining you to what is the equivalent of a monotone railway, then, at least in my opinion, that exposition fairy has failed.
Navi may have been annoying, but you always had the option of just ignoring her and go explore anyway. You cannot ignore Fi however. You will either have to play the game she means it to be played, or turn off the console. There is no alternative.
And that is why, for me, Navi is a better partner than Fi.
