Ask HN: What Node.js web framework do you use?

I am looking to build a new web app using Node.js. The idea is to acquaint myself with some new technologies like ES6 and React.

I have dabbled with Express a long time ago, but I can see that there are now a few more alternatives like Sails, Loopback, Hapi etc.

I was wondering what is the preferred framework for building a small-ish project in Node.