It depends. 8A is closest to the pool and also close to the cabanas bus stop. It is our favorite location. 9B is also a great location, but it is now business class.
If you want to be near the first bus stop picked up and dropped off when going to/from the parks, casitas 4 or 5. Close to the pool - ranchos 7B if you don't want cabanas 8A. Closest to the main building - the preferred rooms (casitas 1, 2 and 3) or business class (9A). Quietest - any of the ranchos, but be prepared for a 10-15 minute walk to the main building.
Any of the cabanas buildings are nice with kids - close to the pool but not too far from the main building.