With close to 400 "played" sims in my main save, most of my worlds are pretty full, and well used.
My go-to world is almost always Willow Creek. I like the historic, small town feel it has, and usually try to embrace it, rather than change it. Most of my main sims I play with always live there. I also have a lounge, a recreation center, a restaurant owned by Bob Pancakes called, you guessed it, "Bob's Pancake House", a library and a dog park. Newcrest is another favorite. I usually use it as more of a place for venues like shops, bars, and cafes than houses. Sims from Willow Creek go there often, as I imagine the two to be quite close, and Magnolia Promenade is the "fancy" area of town with the expensive shops and restaurants. Since I bought Growing Together, I've moved many of my Newcrest venues to San Sequoia.
? I like Windenburg ? (You can't help but sing to the tune of that "Come to Windenburg" song lol), but I don't play in it that often. The Bluffs is my go-to spot for sims going on a date though, and the Von Haunt estate is often used as a wedding venue. Chestnut Ridge is really cool too! I have a barn that's been converted into a night club there. In San Myshuno, I have an arts center, and a rooftop cafe. Lots of sims live there too, and I'll probably add more apartments to it when I get For Rent one day. I haven't figured out what to do with Forgotten Hollow or Moonwood mill yet. Strangerville is also cool for its small town retro vibe. I have a 1950s style American diner there, and my werewolf lives in an abandoned warehouse (were-house?) where the crashed plane used to be. Can't figure out how those Victorian houses in Strangerville fit into my save yet, but they're really nice.
Oasis Springs is usually where my wealthier sims live (since the Landgraabs live there) but I do have a bunch of tiny houses in Johnny Zest's neighborhood. (He's since moved to San Myshuno, and started (or is trying to start) his own late-night comedy tv show.) Del Sol Valley is of course where my celebrities live (except for the two lots near Vanessa Jeong's house. Those are usually where my "fixer upper" type houses go.)
Brindleton Bay is more of a fancier town than Willow Creek and Strangerville. My snob sims hang out at a renovated Club Calico. There's also an arts center there. The museum near the lighthouse is one of my favorite default lots. It's one of only two museum lots in my main save, and I haven't ever felt the need to renovate it.
Tartosa and Sulani are usually for vacations or, for the rich sims who I imagine have their own private jets, good places to go when you're having a boring evening sitting around your 1 million dollar mansion lol. (Thanks money cheats!) The beach in Tartosa is another one of my favorite lots to visit. I'll also probably have some sims live there and make nectar now that we have it.
I hardly ever use Evergreen Harbour, since I can't seem to figure out what to put there. It's a cool world, but I never know how to use it. Copperdale is usually just for the school, but I do have a renovated ThriftTea there as well as another diner. I don't use most of the other worlds very often. Henford on Bagley will probably get used more since I got horse ranch, since its lots are bigger than many of the Chestnut Ridge lots.