"How about" vs. "What about"

I think they can be used interchangeably, there is a lot of overlap between the two, but I would usually use

• "How about" when making a suggestion that I feel is best.

• I would use "What about" when I am less set on the idea and more willing to listen to other suggestions.

"What about" can also express an objection, whereas "how about" does not.

How about going to a movie?

I would love to, but what about the kids? [meaning that we would have to arrange for their care]

See this link and this.

From what I´ve learned teaching English, and what I´ve seen in most books, the difference is that we use WHAT ABOUT + noun, and HOW ABOUT + verb. It´s a pretty simple explanation, but that´s how it´s being taught in schools in Brazil.

"What about ..." is usually a way to bring an objection or potential obstacle into consideration in my experience, whereas "how about ..." expands, rather than restricts, the possibilities."

This is a very good way to describe it. Here are some examples:

Andy: "I'm bored. There's nothing to do." Danny: "How about we go see a movie?"

Andy: "I'm bored. Let's go see a movie." Danny: "What about our exams tomorrow?"

In the first example, Danny expands the possibilities: Andy thought there was nothing to do, but Danny reminded him that they could see a movie.

In the second example, Danny limited the possibilities: Andy wanted to see a movie, but Danny reminded him that they had to study for their exams.

On a side note, "what about" cannot take a sentence. "What about we see a movie?" is wrong. You can say, however "What about seeing a movie?" or "What about a movie?"

I think how about is used when suggesting an idea, which could be answered or not, whereas what about requires answering, but I'm not very sure..