Whats is the difference between 開発途上国 and 発展途上国? What is the difference in the usage of these 2 words? I get the difference between and and my interpretation would be that could refer to a developing country where the standard living conditions are low and are starting to improve, while could refer to a country which is putting emphasis on infrastructure and other advancements. Is one used a lot more over the other? Is there a minor difference in nuance?

They are identical. You can see several dictionaries redirecting to . In that sense, is somewhat more common.