It is much simpler to animate between two classes in straight CSS. That's the primary reason I favor the `className` approach.

I touch on this in a post - I did try the latter, but got a React warning in the console about unmounted components. That, together with a comment in the official docs, made me go with the show/hide approach.

Although as pointed out in the Disqus comment, choosingg what to render is also fine, I probably did something silly stemming from not fully understanding the component life cycle.

Performance, I think.