Every time I go out to move a pile of firewood, I think this is hard labor, but it's not hard work.
The best hard labor is the occasional manual labor you do that tires you out, makes you sore, and it compliments the routine exercises you do in the gym. It's really just another form of exercise.
The worst hard labor is the repetitive manual labor that some of us have to do every day of our lives. This is the type of labor the wears out joints, mangles spines, and beats young boys into weathered men.
Hard work is something different. It's work that's hard to do, only a few are willing or capable of doing it, and it's highly valued by others.
It's probably fair to say, If everyone could do it, it would be called...easy work.
My wife homeschools our eleven-year old twin boys. That's hard work. Going to the office and doing something familiar…that's easy work. I couldn't do my wife's job.
My father always said: "If you never want to work again, find a job you love."
This brings me to the 'best kind of work'. It has to be hard work that you love to do. This kind of work creates the most value and doesn't seem like work at all. If you have to work for a living, then having fun while making money is about as good as work gets.