I have been looking at the reefs occupied and reclamations done by China. Actually China has controlled 12 reefs, more than what media usually mentioned. Count the PRC flags:
The reclamations were done on its 7 reefs, so it seemed to me that each reef was reclaimed based on its geographic and strategic relevance. Although the importance of the largest 4 natural islands in the Spratlys have diminished significantly since the PRC reclamations, those natural islands may still have their maritime entitlements under UNCLOS. Furthermore, 3 of 4 largest natural islands have airstrips, so I get the feeling that the PRC chose those reefs to garrison and reclaim so that they can continue watching over those 3 islands:
0. Eldad Reef: Is PRC controlling and reclaiming this reef?
1. Gaven Reefs (reclaimed): Watching over Itu Aba Island (0.49 sq km, Taiwan ROC, 1200m runway)
2. McKennan Reef: Philippines media kept saying Chinese is reclaiming it but probably they were mistaken for Hughes Reef since both reefs are close by.
3. Hughes Reef (reclaimed)
4. Hallet Reef
5. Empire Reef
6. Whitsum Reef
7. Johnson South Reef (reclaimed): Monitoring south side activities.
8. Subi Reef (reclaimed): Watching over Thitu Island (0.33 sq km, Philippines, 1300m runway
9. Fiery Cross Reef (reclaimed): Going to be PLA command center HQ with a possible 3000m runway.
10. Mischief Reef (reclaimed): Monitoring east side (Philippines) activities, possible runway.
11. First Thomas Reef
12. Cuarteron Reef (reclaimed): Watching over the Spratly Island (0.15 sq km, Vietnam, 610m runway) and south west region.