> Kitze was kidding (I hope), but for a while this was a very real debate. Especially when render props were first taking off. Since then, Hooks have made anonymous (inline) functions even more popular.

Isn't this missing the point? It's not about the overhead of declaring a new function, it's that you've made one of the props change on every render, so your child element needs to run its render function every time. The render function of Number only has to create a single H1 element which doesn't seem like a good test.

And the ExpensiveComponent example is strange to me. It's being memoized, so what exactly is the point?