It also depends on how you value your reward.

In short - Citibank US Thank You program is better than its KR counterpart (which should be named as Thank You as well). So if you think you can afford it (not sure if you make USD or KRW), then using the U.S. card is a better option.

To make it simple - almost all Asian cards sucks. It is only a matter of how suck they are.