If I had nothing but time I wouldn't mind a 14-day RT voyage to Hawaii to see the islands, but I personally think Pride of America is a very good ship and itinerary.
They understand you are not there for the cruise experience so much as you are there to see hawaii, and so they are in port every day, and last time I checked the are overnight in every port (except Oahu, but you can arrive early to see it).
They give you the full Hawaii experience.
I have heard airfare to Hawaii is up lately, and that is too bad. The normally relatively cheap air is one thing that makes Hawaii such a fun place to go.
If I had to choose between HAL and Celebrity, I think I would prefer one of the newer HAL ships with a movie theater, the MicroSoft classes, the culinary classes, the Exploration Cafe, etc. They are small but active ships.
I also like Celebrity - but find the smaller ships to be a little too quiet for me.