Le Fanu said:
I would say Faeries Oracle as it came first and I guess that - like it or not, intentional or not - The Heart of Faerie must surely build on the Faeries Oracles. I don't have Heart of Faerie but it feels like a sequel.
It is not a sequel.
Although they were made by the same artist, each deck has a completely different 'feel'. Like Faunabay would say, the "Faeries Oracle" has the country/wild faeries, and the "Heart of Faerie" has the city faeries.
I personally like the Heart of Faerie much more than the Faeries Oracle. I like the elegant and soft energy of these faeries... But I know that it's not true for most of people - most of reviews claim that the Faeries Oracle is better, specially because of the companion book written by Jessica Macbeth.
Tanjamuse, I suggest you search for pictures of the decks. See which one attracts you more, and then if you want to make sure that the deck is what you expect, look for some reviews. Both decks are very beautiful and worth having, and you can even use them together.