For me "working smart" has two meanings. First one is that "smart" refers to those kind of work, that require you intellect, rather than physical exercises. Intellectual work isn't that difficult, comparing to physical, but it must be appreciated more. And the second meaning, "smart" may also refer to the way you do your work, not the nature of work: you need to find useful contacts, you need to know how to plan your time, you have to be orderly and know how to present yourself.
Personally, I don't think it is the right approach to distinguish between hard work as mostly physical and smart work as mostly intellectual, though it should be clear that when your work involves physical part, for example, as a mover, there is not much you can do with it, I mean, doing it in a smarter way. So we are basically left with intellectual work involving your brain, and that's where most of the distinction should be made between working hard and working smart since you can use your intelligence in a smart or dumb way.
I was about to pint out this thing. We need both attributes in life to be successful from every angle. If the person is hard working but not smart, again it is going to cost him much of the time and other resources to meet the deadlines. On the contrary, if the person is just focusing on being smart and not paying any attention on working hard, he or she is again going to suffer because simply buy understanding things, you cannot score well, you need to grasp them by hard working.