Every user here will have a different opinion about the HI resorts.
We have kids that grew up vacationing in Hawaii.
When the kids were little, Ko Olina was the place because the lagoons were suited to them.
As teenagers, they love Waiohai and Poipu beach.
At Waiohai, we see the exact same people there year after year, and have developed strong relationships. You should also be reading from that statement that Waiohai owners tend to stay there (meaning they tend not to deposit in II). Being a non-lock-off resort also means very, very few Waiohai deposits.
Ko Olina is so big that every time we go there it's new faces.
If we ranked them it would be:
1. Waiohai
2. Ko Olina
3. Maui Ocean Club
4. Kauai Lagoons
5. Kauai Beach Club
The first three are steps away from the water.
Ko Olina has the best views and arguably the best pool. It is also on the quieter western part of Oahu. Much less hectic than Waikiki. Bad thing about Ko Olina is that there is no beach nearby; the four lagoons hardly count as a beach.
Waiohai has Poipu beach; Maui has Lahaina - both spectacular beaches.
Waiohai is very laid back. "Feels more like Hawaii" than the other locations.
Maui Ocean Club is in busy Lahaina; take that as a pro or a con.
Kauai Lagoons is too isolated. No nearby beach.
KBC has a good location and OK beach but the rooms are converted hotel units. They were not a big hit with my family.
Why not rent a week at each and see how they feel? You cannot go wrong at any of the three you are considering.
And as multiple people have consistently said - don't buy Hawaii to trade in II. The MF are so high, anything you trade for will be worth less.
Do not think that just because you own a 2BR Ko Olina OV that you will easily trade into Waiohai or vice versa.
II does not get a lot of Marriott Hawaii deposits, so they likely will not have something to trade to you. Plus, owners are more likely to deposit their studios into II; you will not see many 2BR deposits.
And if you own an Ocean View unit and deposit in II, you will get an Ocean View at the other resort, right? NOPE! View is moot once you deposit.
I don't think this point of low II Marriott Hawaii availability is sinking in quite yet.
In terms or buying resale, things to consider:
Waiohai and Ko Olina are about the same in current sales prices. Maui will be more expensive, as will anything you do in Lahaina.
Ko Olina and Waiohai are the lowest prices I have ever seen. It's a good time to buy. If they dropped by half, you would not be out much $$.
It was not that long ago that 2BR at either was $18,000.
At Waiohai, your options are very simple: 2BR Island View or 2BR Ocean View. And Waiohai has no lockoffs.
At Ko Olina there are more options 1BR, 2BR, 3BR, Penthouse, and for each Island View or Ocean View
At Maui, there are many options. There are two Maui Ocean Clubs, each with a different tower. 1BR, 2BR, Island View, Ocean View, Ocean Front.
And of course for all of the above another option is EOY or Annual...