Nextjs: static class / use function

I want to create tools class/function in nextjs

I have 2 ways for this.

With static class:

class Tools {
    static titleCase(value: string) {
        return value.charAt(0).toUpperCase() + value.slice(1).toLowerCase();
    }
}

export default Tools

With use function:

export default function Tools(){
    function titleCase(value: string) {
        return value.charAt(0).toUpperCase() + value.slice(1).toLowerCase();
    }

    return { titleCase }
}

And here is my question:

1- Which is better?

2- What is difference between these?