[recursive]

For functions of single arguments, you parameter list parens are optional.

But it's not an objective fact that coffeescript's syntax is better. I prefer ES6. And even if you prefer coffeescript, it seems strange to claim that the most critical feature is purely aesthetic.

[briandear]

Assuming it's all ultimately JS, the aesthetic side is a big deal. It results in an easier time understanding and being able to debug the code, which is a huge, perhaps underestimated win.