Japan or China for a Culture Trip?

For those who have been to one, the other, or both, I’d like to know which of these two countries feels more distinct from the US and why.

Please pardon how cliche and idealistic this sounds. I’m one of those cheesy, existential travelers who loves to experience a culture so distinct from mine, that it serves as a waypoint for analyzing my American way of life. The further the waypoint, the greater the opportunity for self-reflection.

For example, going to India and learning the “go with the flow” approach to life was mind blowing. The friendliness and contentment with having very little in South America was another cool cultural value I loved as well.

Between Japan or China, has anyone gained any change in perspectives from one more than the other?

Thank you in advance!