Some considerations:

American Airlines miles allow you to fly on American Airlines or Hawaiian Airlines metal, or a combination of both. This is important. Last time I flew to Hawaii, neither airline could give me an award ticket on their metal only, but American could put me on a Hawaiian/American combination. (Hawaiian was by far the better airline - they actually served me a hot meal!).

I am not sure if Hawaiian will put you on American or a combination. But if you have leftover miles, the American ones will be more generally useful. They can be used to get you to most anywhere in the world. American also seems to have the most availabiliby of award seats over any other airline, with the possible exception of Alaska Airlines.

United airlines nonstop flights to islands other that Oahu cost 10,000 miles less than both United and other airlines charge for flights to the same place, stopping in Honolulu. But United award tickets to Hawaii are much more difficult to obtain.