Can I ask what you love about Casitas 4? We have teenagers, so don't need to be right next to the pool. My thought was that Casitas might be a little bit quieter, while still not being too, too far from everything. (Don't want to be way out in Ranchos).
First off, I use the fitness center. So being in the same building is a big convenience. It's a 3-4 min walk to the food court. Right by the first pickup bus stop. The quiet pool is very big, it's twice the size of the other ones, it might be the largest quiet pool at WDW. There are a large amount of lounge chairs and tables in this area. It is a great place to hang out both during the day and at night. We never bothered with the main pool the one trip we stayed at this location.
We've stayed in the Business Class rooms since they were a book able category, but there were none available this time. So we went with a standard room and are hoping for Casitas 4. Which is are second favorite location next to BC.