Some of the features of ES6 are pretty neat. Some of them are just crap piled on crap, which bloat out the language for marginal benefits at best.

Unfortunately, many of the ES6 features inspired by CoffeeScript features are completely unoptimized and an order of magnitude slower in cutting-edge browsers than the CoffeeScript versions. Even more unfortunately, they don’t work at all in lots of browser versions people are still using today. Which means that they can’t really be adopted by most projects yet.

Finally, even if ES6 were implemented perfectly everywhere, it’s still much less pleasant (from a syntax clarity perspective) to read and write ES6 code than CoffeeScript code, at least for me.

At the point when the vast majority of browsers support ES6 features, it will perhaps be reasonable to change CoffeeScript to use them in its generated output. In the mean time, CS is fantastic as-is, and its generated code works efficiently in every browser.

But hey, use whatever language you like (ClojureScript, Elm, Dart, Haxe, ES6, whatever..). It’s your code, so the only people who should care are you and your close collaborators.

So use Babel, as long as you're using a compiler anyway?

Not my personal cup of tea (I don’t particularly like the ES6 syntax, and as I mentioned many of the nicer features are horribly inefficient in current browsers), but use whatever you like!