It's an insider vs. outsider thing. While an 'insight' implies an accurate understanding of something, an 'opinion' is not necessarily based on experience or knowledge - it may even be obviously false. read more
An insight can be an opinion. For example, last spring I took a philosophy class at my university. I would describe the class as insightful; it taught me how to think and unravel arguments. read more
As nouns the difference between insight and understanding is that insight is a sight or view of the interior of anything; a deep inspection or view; introspection; frequently used with into while understanding is (uncountable) mental, sometimes emotional process of comprehension, assimilation of knowledge, which is subjective by its nature. read more