Knight or Bishop?

I posted a comment in a forum with a game that asks the question:  Is the Knight better than the bishop? I have played a game where it is not clear whether which one is better and it is particularly funny to me that I recently just played this game on Live Chess, at the time this forum topic was posted.  Coincidence or not?  Take a close look at moves 19 - 21?  I am completely in position to take my opponents queen with either of these pieces.