To be honest, I always wondered why there were no Animal Crossing spin offs. I mean, the first Animal Crossing came out in 2002 (?) so that's 13 years till they started making spin offs. I haven't played amiibo festival but I have played HHD and it's a lot of fun in my opinion. I just don't understand why they haven't made an Animal Crossing for Wii U yet and I have kinda lost hope they will make one for Wii U.
Well, they've had apps in between though, first on the DSi, later ported to 3DS, and the Plaza on Wii U, which is now no longer available, but the did get stuff other than the main games. You do realize the only reason ND Cube made Amiibo Festival (yes, they were the ones who made it, not the actual Animal Crossing development team) was to implement amiibo- Kyogoku wanted amiibo, but sheesh, what a bad way to implement them! It was so bad, the sales tanked (many stores are now putting AC figures and cards on clearance!) that they resorted to updating a game turning 4 soon (in Japan) to get people to buy the amiibo! The Wii U is on its final stretch run, its got a low install base, and since console versions of Animal Crossing don't sell well (to get an idea how bad they sell, the spin-off game HHD is about to outsell City Folk, the highest selling console version in the series!), so don't expect a Wii U version beyond AF, or rather Amiibo Cashgrab.
As far as both sucking, you've got to understand they totally are aimed at a VERY specific genre of player, one who has an insane love of Animal Crossing, willing to pay HUNDREDS of dollars for the amiibo/cards, because these games were made just for them- yes, you DO need the cards in HHD if you want all the furniture, because the special characters furniture (ie Isabelle's scooter from Mario Kart) are only unlocked using their cards/figures. It's clear they just wanted to implement amiibo, what Kyogoku later admitted (like that wasn't obvious already with Amiibo Festival), and it got so bad, that not only are stores putting them on clearance, but Nintendo is updating New Leaf to use them in hopes that people will buy them, because their sales are totally tanking! Hence why stores are putting them on clearance, people just aren't buying them.