If we consider that the moderation of climates occurs due to the Ocean, we know that the most moderate climate will be near the ocean. This helps narrow it down a little. This means that East Asia will have the most moderate climate. If we want to narrow it down even more, we can look along the coast of China and South Korea. There is no right answer as this is subjective but I would have to say that the coast of China and South Korea has the most moderate climate. Busan, South Korea is a good example.
