Let's call it super audio-only. When you talk to someone on WebCall, their voice will be clearer and more present than it is in most real-life situations. This alone is worth everything.
But there are many other aspects. Whenever you call someone on their phone, you interrupt that person in the middle of something. When you set up a call with Duo, you give the person a bit of lead time. I love this.
In the future, telephony will be much better than what it is today. And it won't be video.