Owning HI for the purpose of staying there most of the time is good - you will always get the week you want. However, using it to exchange is usually not great, as the MF are often higher than what you would pay to rent the other destination, and ALWAYS higher than the cost of a getaway. As stated before, the HI Marriotts are better than most II destinations. In other words, you are almost always trading down. And if you buy OV Ko Olina, you will pay even higher MF and will lose more in the trade, since II doesn't consider view.
Renting out MKO and using the proceeds to rent into your desired destination is wise; you will usually come out ahead. Depending on season, MKO OV can rent easily for $3500.
There is a benefit of owning two Marriott weeks - that you can reserve your week 13 months out instead of 12 weeks out.
The flip side is that you need to reserve consecutive or concurrent weeks.
The reason this matters is that you would THINK that as an owner you can always get whatever week your deed entitles you to get.
The reality is that the most popular weeks at the most popular resorts get reserved 10-15 min after they become available. You want to stay at Ko Olina on July 4th weekend? So do a LOT of owners, and they reserve the second the week becomes available. At least at Ko Olina, HALF of the inventory is released 13 months out. The good stuff gets snatched up quickly by the multiple weeks owners, but it takes a few days. Then there are poor souls who at 12 months out fight over the remaining half of the scraps. And there are those owners who only want those hugely popular weeks so they can rent them out for max profit. You want to stay at MKO only in February or October? No problem. You can get that easily; don't need the 13 month rule for that.
Owning HP and MKO would technically entitle you to reserve 13 months out, but that wouldn't work well with your vacation plans since they are two different regions. So to use the 13 month rule you'd probably have to reserve one for rent and one for use. (i.e. reserve both for Jul 4th weekend and rent one while stay at the other). That's why many people own 2 weeks at the same resort.
You CANNOT, say, reserve MKO 13 months out and then reserve HP , say, a month later. The reservation has to be for both weeks during one phone call. ALSO, if you have EOY deeds - say an even HP and an odd MKO - then you can't use the 13 month rule at all; the deeds would have to both be even or both be odd. And in case you're wondering, splitting a week into 1BR+studio does NOT entitle you to 13 month reservation. You need two deeds. The rule was created to urge single week owners to buy another.
If this 13-month thing is news to you -- research it and use that knowledge for your second choice. It can be a huge benefit if used correctly or a nothingburger if you have the wrong plans. See this
thread that explains the rules.
In fact, learn everything you can from
this thread. It's the Book of Marriott in the Timeshare Bible