That`s because there are many ways (hand positions, finger positions, top-down or bottom-up) of doing an in the hand faro. Some prefer doing it from the top down, others from the bottom up. I can do it both ways and practice both because sometimes the decks have a different cut (traditional cut is best used for bottom up faros if you want the deck in a face-down position to start with. It`s also the prefered cut for table faros.) and I most often want the deck face-down (otherwise I could just flip the deck but I don`t want this).
Overall I would say the "top-down in the hands"-faro is easier for most. In the end it`s up to your personal preference.
You can find good descriptions in Card College and Close-up Card Magic, and Michael Close has a very good download on the faro.