Never played Brawl, so I can't say if this is better than Brawl's Animal Crossing stage, but I would preferred they did what they did with the Mario Sunshine stage, but set it in a random town and fight on the rooftops of villagers houses and town buildings.
This one will only be on the Wii U version of the game. I imagine that if the 3DS version has an Animal Crossing stage it'll be based on New Leaf. I don't see why there won't be, it's one of the most popular games of the year already.
It does look more detailed, Albeit I have no idea if it'll use the Wii U or 3DS Clock as a compatible system to the stage like they did in Smashville stage on Brawl.