Laravel json response: response()->json() or $var->toJson()

I'm using Laravel (in fact Lumen) for my API. I have created a User model and I use this to retrieve all my users:

$users = User::all()

Now I want to return it as json but when I read the Laravel site I see two options. Which one is the best and why, and what is the difference?

return response()->json($users) (as described here)

return $users->toJson() (as described here)

via Chebli Mohamed