They are almost interchangeable. I use both after I give information about myself. I work as a nurse. How about you? I like to swim. How about you? I have 3 brothers. What about you? Simpler way: just say: and you

It is roughly equivalent to "y tu?" but a bit more formal!

Hi Nathali, Most of the time they are interchangeable. If used when expressing an opinion then i’d say that you can use either. I don’t like the cold, how about you? / what about you? However, what about you could also be used like this... What about you do you dislike? Or What about you do people first notice? These are not the best grammar but nobody unless an academic would question them. I hope that this helps :)

Sorry I missed the second part of your question. I would use both after I have given information about me. I work as a teacher. How about you? I love to travel. How about you? I have two sisters. What about you? You can also simply say. "And you?"

Hi. Honestly they are interchangeable questions.