E.g.
- I'm going straight home after work. How about you?
- I'm going straight home after work. What about you?
They both seem to work interchangeably, but there feels like a subtle difference and I can't quite pin it down.
Similar but a little bit different from "How about" vs. "What about", the same arguments do not apply because we are always referring to "you".
Best Answer
As a native English speaker, I feel they have different implicit meanings. Without knowing the context, this is how I interpret them:
I'm going straight home after work, which I assume you are also doing, would you like to accompany me as far as it is possible to travel together? Or, can I give you a lift?
I am going straight home after work. You are not invited to join me, and I am not interested in doing anything with you, but I expect you will not be going straight home and I am curious where you are going instead.
John Lawler put it excellently in his comment above: "'What about you?' requests a statement about you in general, while 'How about you?' requests a response about your manner, means, or condition."