Honolulu (on the island of Oahu) is Hawaii’s main city and so you would get all the benefits/drawbacks of that–meaning, there’s going to be the most stuff to do on Honolulu, but there’s also less of the sort of “pastoral” vibe. If you’re a person who doesn’t want to be on a beach all day and like having some city-life (shopping, arts&culture, nightlife, etc.), then Honolulu might be a good choice. It does have beautiful beaches, but you know, it’s still a working city. I also think that in terms of the swimming quality, Honolulu has among the best options–of course all of Hawaii’s oceans and beaches are beautiful and you’ll find great sandy beaches on all islands, but generally Kona has a rockier shoreline and Kauai’s waters can be downright dangerous, for example. I admit, my family is from Honolulu and so I’m a bit biased, but one thing that drives me nuts is when people go to Honolulu and claim it’s “tourist-y.” Waikiki might be “touristy” but again, Honolulu is a city, and no more or less toursity to me than New York is–it depends on where you go. Oh–but bad traffic in Honolulu. Like, seriously bad traffic ;(
Both Kauai and The Big Island (the official “Hawaii”) are quite rural. The Big Island has the active volcano, which gives it a unique landscape–you can visit black sand beaches and hike nearish to the lava flows. The Big Island’s two large cities, Hilo and Kona, are also quite different in terms of their ecology–Hilo is the “wet side” and very rainforest-y (lots of State Park hiking if you like that sort of thing); Kona is the “dry side” and very …dry. Most of the big-name hotels are in Kona lining the shoreline, but TBH, there isn’t that much to do in Kona aside from being at the resorts (not that that’s a bad thing–most of the resorts are absolutely gorgeous and a lot of them have all kinds of entertainment right there–water slides, boat canals, luaus, I think the Hyatt Waikoloa has a dolphin lagoon (?)). There’s some tiny local development and the coffee plantations, plus a little nightlife along the coast, but it’s all kind of touristy. If you like to golf, however, the Big Island has some great courses.
Kauai is trendy these days because it’s also quite rural and more “natural” feeling–very green, lush island, very beautiful. Again, lots of hiking (with waterfalls and tidepools and all that); good snorkeling; great surfing–although, you have to be careful with that because local spots are definitely LOCAL. But, it’s also somewhat rural. Like, Kauai has a rooster problem and you’re likely to see wild roosters on the beach and hear them crowing in the mornings kind of rural. My family members have had issues with wild boars eating from their fruit trees kind of rural. Outside of Hanalei in Kapa’a or Lihue, things tend to shutter up at like, 8pm. Most visitors like to stay on the north shore (which is where a lot of the hotels and timeshares are) and the main town there is Hanalei–which is cute, but also tiny. And again, Kauai’s beaches are not for the faint of heart–riptides, high-surf, reefs are all common around Kauai. Stick to “established” beaches because you don’t want to take a dip just anywhere. But, like I said, Kauai is popular for a reason–it’s gorgeous and pastoral and more natural/private-feeling. Never met a person who went to Kauai and didn’t like it!
I can’t really comment on Maui because the last time I was there I was like, 10, except to say that we went to Haleakala to watch the sunrise and then hiked down into the crater and that is still one of my favorite memories.
Also 2nd azbee:
‘s recommendation to think about island-hopping. Most mainland flights go into and out of Honolulu anyway, and it’s such a short flight to the outer islands (and usually fairly cheap) that hopping to one more is probably a good experience. Honolulu + 1 other island is probably enough for 1 week, but I’ve heard of people doing 2…
One last thing I forgot to mention: all of Hawaii’s beaches are considered public. That means that you don’t have to stay at a specific hotel to access the portion of the beach that hotel is on. You can literally walk straight through the lobby of a 5-star joint wearing a big inner-tube and park it on the sand next to the hotel guests. Pools and stuff are another matter, but the hotels are generally required to provide public access to the beach (even billionaire socialite Doris Duke couldn’t get her own private dock–you can still see local kids using it every day after school!)