There is a depth to Korean culture that is not obvious at first sight and I think some of the superiority feeling comes out of that, not insecurity.

The insecurity surely also plays a role but I feel the core of Korean national ethos is in this all-encompassing philosophical and ethical structure of advice, rules and traditions.

China has an equal and longer tradition but maybe more elements and variety due to sheer physical size and different ethnic backgrounds.

This is not something based on academic observation. just a gut feeling that has developed during the years.