I currently own at Lawai Beach and the Cliffs and have stayed at the other three resorts you mentioned. Wyndham Bali Hai is right across the street from the Cliffs. In fact, recently I spent a week at Bali Hai and then moved across the street to the Cliffs for the next week. I stayed for a week at Wyndham Ka'ei Kai a number of years ago but despite looking quite decent on the outside, it was quite run down at the time. I swore I would never return. Hopefully, they have fixed the roofs, the sliding doors, the insect infestation and a host of other problems.
Lawai Beach Resort is well run. The people who work there are great but there is often re-construction going on due to a 'spalling' problem. I like the location of the resort and find that it is central to most daily outings the you can plan. Kauai Beach Villas was different. Some people may prefer Kauai Beach Villas but I prefer Lawai Beach Resort.
Of the five, my favourite resort is the Cliffs. I own a loft unit and usually get a great view of the ocean. If you can choose two of the five (e.g., if you are there for
two weeks), I would choose either Bali Hai (which is very nice) or the Cliffs (which I prefer) for one week and one of the other two in the south. Princeville is a different experience than Koloa (or the southern coast). My least favourite area is around Kapaa (I find it too congested and busy). Others may not agree with my choices and I respect that. I have been to Kauai so many times that my game plan now is to just relax and de-stress. I have done several helicopter tours, excursions, hikes, tours, etc and unless something really inspires me now, I just go for long walks, enjoy a few restaurants and take in the beauty, the color and the great Hawaiian spirit.