I translated a whole project from ES5 to ES6 and the experience was glorious for two main reasons:
But.... on the other side about use ES6 is that now the project has a lot of dependencies that I wasn't using before, and in the end I Just was using Arrow Functions from the new syntax (of course, I used clases, weakmaps, and a bunch of others, but the arrows are everywhere)
My recommendation is to use it only if you're sure you are needing all the features that ES6 brings with it, cause you'll have to change your code style, and your build process in order to compile and serve the files.