South Korea has slapped its own face by admitting that SM-3 is better than THAAD.

http://en.people.cn/n3/2017/0913/c90000-9268579.html

If SK understood that SM-3 had better performance than THAAD, then it shouldn't install THAAD in the first place and irked China & Russia.

Why did SK install SM-3 after THAAD? It's pretty obvious that THAAD was useless against NK because the motive for THAAD was to help the USA to monitor China & Russia using the THAAD radar.