The Froud decks have a very particular energy about them. They are definately not all 'love and light' like a lot of the new agey fae decks are. There is more to the elemental realm than butterfly wings and bubbles. But then I grew up on Froud\Hensen collaborations so I was doomed to love these decks from the start.
I first bought the Faeries Oracle in 2003 in a quest for a non-tarot deck that had some kind of depth to it. I got so sick of decks made up of a handful of cards with single word entries on them. Thats fine for some, but I like specifics! The Froud decks (I have both now) are laced with meaning but its in a certain code that challenges you to stretch yourself with each reading. Nothing is ever straight forward, its always a labyrinth and just when you think you've cracked it. No! Hats not what we meant at all... is what you'll hear. The deck challenges you to overturn your assumptions and to not learn cards by rote but by direct experience with the forces represented by them.
I love these decks for this reason. But they are decks that require commitment and a personal relationship. Its easy to get frustrated with them especially as they continually throw up cards at you repeatedly regardless of the question if you're not getting it. These decks answer the question that must be asked, not necessarily the question you are asking. These are the only decks I've encountered with a real life of their own.
The app deck is just okay for me. It'll do in a pinch, but its horribly limited and doesnt allow you any real freedom to construct a reading. But if you need to just pull a card in the moment it will do without carrying the deck in your back pocket.
Now the difference between the two. HOF contains more of the seelie and unseelie court than the original deck did. I find its a more relationship (relationship to others and self) deck than the original. The FO deck has more scope for general questing. I have bought both and will combine the two. Sometimes I will make up a deck for purpose by choosing certain cards from each, or I can use all of them. The fae realms aren't sticklers for rules, they like fluidity and a certain amount of chaos. That use of the cards would be perfectly acceptable and even encouraged by the energies presiding over it.