I love the GH Kauai. I love the staff, the suites, the pool.The Club is lovely. I am not such a fan of the island though. It is beautiful, but we didn't find a big choice of things to do.
I love Maui, the island.
I love the staff at Hyatt Maui.
The suites are OK.
The cabanas are great, but expensive.

If you just want to stay at the hotel, then Kauai is great.
If you like to venture out, then Maui is better.
Just my opinion!