I have both ACWW and ACNL.
Where to begin... the beginning? Ok. In ACWW you have to be Nooks unpaid intern during the tutorial, then after that you're in the game. Everything is available, except Nook's shop is tiny, Harriet isn't present, and Brewster and Sable won't chat with you. In ACNL, the game starts out slower and it takes quite a while to unlock some features. Isabelle, the town hall clerk (my theory is that she was intended to be the mayor, but chickened out, and instead has you do her work for her.) ... what was I saying?... Oh, yes, Isabelle suggests some tasks for you to perform. This is your tutorial. Timmy and Tommy's shop is tiny, and doesn't sell axes or watering cans. The shop that sells those items isn't unlocked until you've demonstrated your genuine interest in gardening and landscaping. Still Harriet isn't present, but neither is Brewster. I've been playing two weeks now, and still haven't unlocked the cafe. Nor have I unlocked the room where K K Slider performs. Sable still doesn't chat with you, initially. But as with ACWW, she will begin to, eventually.
What I have unlocked is the Happy Home Showcase (where a model of your home is shared to others via streetpass.) When you visit a home in the showcase area, you can view the exterior, and tour the interior. When inside any room, you can order any of the furniture or decorations, etc that is on display in that room. (Note: you can't order special items... using ACWW items as an example: you wouldn't be able to order any of the mushroom or snowman -themed items, but you could order that *&%&^$& Robo Lamp you've been waiting for, for over 3 years to appear in Nooks shop or Redd's tent.) I've also unlocked Tortimer's tropical island. The round trip boat ride costs 1000 bells, but it is so worth it. The place is swarming with exotic beetles. Seriously, you should be able to rake in about 250,000 to 400,000 bells during a single trip there in the evening (after it has started to get dark.) From the main island, you can go on a "tour" where you participate in a minigame. If you do well in the minigames, you're rewarded with the local currency which can be used to purchase items from the main island's gift shop. During some tours you can smuggle back exotic fruits or flowers to the main island, and from there to your town. (I currently have several lemon trees growing in my town.) Yesterday I unlocked the Dream Suite. When you use it, you can virtually visit someone else's town. (You have to opt in to share your town to others, so it is possible to keep your town private.) It's a "virtual" visit because any "damage" you do isn't actually inflicted on that person's town. You also can't buy, sell, import, or export items to / from the dream town. However it's still very interesting to see what others have done. This morning I dream visited a Japanese users's town and saw some of the things I've yet to unlock.
Perfect town? In ACWW this was determined by number of trees, flowers, weeds, and garbage per in-game acre. I'm not sure what determines a perfect town in ACNL. I imagine these factors are included, but then there's also "public works": bridges (your town has only one when you start), water fountains, street lights, fire hydrants, park benches, etc. These seem to add towards the "value" of the town. I'm not sure if the town's value is a factor towards it being "perfect". As you would ask Pelly or Phyllis in ACWW about how the town's citizens feel about the state of the town, in ACNL you can ask Isabelle. Her answers are typically "it's so-so, but needs more development".
Blathers. It's possible to request him to evaluate multiple fossils all at once, and to accept multiple donations all at once. (And items that have already been donated can't be selected to be donated again.) This speeds up the amount of time it takes to deal with him, but even when you do one-at-a-time, he has much less to say about each item he has identified or accepted for donation. He doesn't really live up to his name any more. (Some may like this, I kind of miss it.)
I've never played ACCF, so maybe the trend was already there, but in general it seems that compared to ACWW, in ACNL each non-citizen character does fewer different tasks and is more focused on doing a specialised task.
As I mentioned, I've spent years playing ACWW and have now spent a few weeks playing ACNL. In general I find ACWW is comparable to a vintage virtual pet. Pick it up, get the chores done, then put it down for a while. You can play ACNL like this too, but it seems like there are so many things you can do, that if you want to just "play" you can do that too.