Agree to disagree, I think in order to succeed you need both. When people say that when you work hard you are only making your boss richer. Personally, I think there was a time when your boss needed to work hard AND smart in order to build a business. In short, you can't succeed by working hard or smart, you need both. If you have neither of it, you'll probably be exhausted and poor.
I understand what you mean by working hard here but for the sake of simplicity and better understanding of the differences between the two, I think we should rather specify working hard as doing the same thing again and again probably putting more effort into your job but without thinking too much over it. With time, you can become more efficient and likely do more but that alone won't make your work any smarter. As Albert Einstein allegedly said, insanity is doing the same thing over and over again and expecting different results. So working hard can't take you any closer to working smart on its own.