I would say that Ko Olina is the least stable since it is heavily dependent on tourism. It has the most fluctuation in prices.
Mililani Mauka is a little further from H-1, but most people I have talked to there really like it. It is more of an established area and a master planned community. Ocean Pointe is still having growing pains. The commute has gotten better, but there is still a lot of traffic. Why not check all three? They are relatively close together and could be surveyed pretty well in one weekend,
I have sold homes in all three areas. Have you visited each of them? You can some great buys in the price range you mentioned. Give a ring at 808 723 0900 if you would like to talk about it more.