The Sheraton is fairly new, but it has small rooms, because it is a remodeled hotel. It's in a great area, (Poipu) but it's across the street and behind the Sheraton Kauai Hotel.
The Westin Princeville is one of Westin's newest resorts and they are full-size condos. Beautiful property in Princeville, Kauai, up on a bluff, overlooking the ocean.
Some people will prefer one, others will prefer the other one.