The difference for me is that the Froud faeries are much more personal.They have volunteered to help,to be in this deck.Jessica Macbeth writes beautifully,and with great humour,in the book that comes with the deck.She and Brian Froud are very talented people and seem to be in personal contact with this Otherworld beings,and help us get that contact to.
The Fairy Ring is not so personal.The fairies are not all helpful,in fact,some are harmful and not to be contacted.I don´t find the readings as helpful,friendly,and loving as with the Froud Faeries´Oracle(although both can be very to the point).The book is very useful for fairy lore,but not as good on divination as Jessica Macbeth´s book.There are good meditations for the fairies who like people.
link to Jessica Macbeth´s site;
http://home.earthlink.net/~jesamac/index.html
and to Brian and Wendy Froud´s site (free reading available,but without reversed cards,or what Jessica has to say about each faery:
www.worldoffroud.com
I must add I love both decks,but I find Froud´s faeries easier to get in helpful contact with.