In short, speed of development and the open governance structure seem to be the two key advantages of io.js. io.js is on a very fast release cycle using semver

In short, speed of development and the open governance structure seem to be the two key advantages of io.js. io.js is on a very fast release cycle using semver for versioning. The don't maintain the node.js concept of a "stable" and a "development" build (e.g., 0.10 and 0.11). Node.js developers want to use a "stable" release in production, and so were stuck on 0.10 for over two years. io.js is integrating the latest v8 and libuv releases, giving developers access to new ES6 features (and enabling stable ES6 features by default). Node.js developers as stuck on an old V8 with poor ES6 support, requiring transpilers like babel. io.js also now has significantly more core contributors than node.js. For what I understand, Joyent only had 1 dedicated node core developer for a long time.