谢邀。这两个词组在一个情况下可以互换,那就是"提建议"的时候。比如,What about a cup of coffee? 和How about a cup of coffee? 都是来一杯咖啡怎么样的意思。
但是,what about的另外一个适用场景,是在谈话中想提起一个新的话题时。比如,A: Oh the food we had last night was awesome! B: Cool! What about the concert? 前面说了吃的好,后面问音乐会怎么样。
How about,更口语化,用来询问某人或某事。比如,I need a drink. How about you?
希望能够帮到你。