I am not sure about the advantages of the suite over a room in the Hawaii building (maybe a second bathroom and a separate sitting area??), but if you are interested, you can see the view we had a few weeks ago while staying at the Polynesian, LVC. Especially since you said the view was important to you, as it was to me, and probably to most people who choose Lagoon view
The link is below, look for the link that's for the Polynesian review. I hope you enjoy!
P.S. I just got this info from Disney World's web site, it doesn't have much info about the suites, maybe you can call for more info, but here goes:
Suites: maximum 5-9 Guests
Stay in a one bedroom with separate sitting area and wet bar (sleeps 5); two bedroom Princess with 2 baths, separate sitting area and fridge (sleeps 9); or King Kamehameha with 2 stories, 2 bedrooms, 3 1/2 baths and kitchen (sleeps 6).
P.P.S. One thing I do know is that the Tonga building sits further back from the lagoon than the Hawaii building does. I know that the suites have views of the castle, but not sure how much of the lagoon you would see (the Grand Floridian, Contemporary, etc, or if that would even be a factor for you). The Tonga building is VERY close to the Great Ceremonial House though.

Personally, if the view is a big thing for you, and you don't have a part of 5, I'd go with a lagoon concierge room.
