I just hate it when people call City Folk a Wild World port, just because it shares roughly 50%. Wild World was without real world holidays like Christmas (Toy Day), Halloween, etc. However, Wild World was a real well written game. I mean here some of the stuff the villagers told you, like after they completed a set their HRA score skyrocketed, or when the normals talk about Mopina. Or, like when Marina says she's into seafood, given she IS seafood- great writers on that game!
Now, to answer the question, it's really the handhelds that are my favorite- Wild World and New Leaf. The games work perfect on them, because of the real time basis of the game. WAY too hard to rush home to make an event, and without time travel I'm pretty much stuck if I miss it. With the game on handhelds, I have YET to miss an event, I've missed them in Animal Crossing, I've missed them in City Folk, but in Wild World and New Leaf, I have NEVER missed an event, it's perfect on handhelds!! Also, I just totally refuse to adjust the clock, unless I'm traveling, and enter a new time zone, then I'll set the DS/3DS, otherwise, I do NOT believe in setting the clock to make up for a missed event, it's STILL cheating to me, because in real life if you miss something, you can't go back in time, and redo it, you snooze, you lose.
So, really to answer, it's between Wild World and New Leaf. New Leaf brings back real world holidays absent in Wild World, and the island in the original, as well as the city from City Folk. It's a perfect combination, so it wins out over Wild World's great writing. Now, don't get me wrong, I still play Wild World (yes, almost 10 full years later), but New Leaf has not missed a day yet, and with the added advantage I already mentioned earlier about being on a handheld, I'll easily make my goal of 1,000 days played by early 2016.