Hard work can take you far but being smart can take you anywhere. That is the difference of those two. Hard work can give an opportunity for us to afford all the things that we need but if you will become smart then you have a bigger advantage because you will see things in a bigger picture and you can easily adjust and implement strategies because you understand the game better than anyone else in your competition.
You need both, there are many persons that are really smart out there that are really lazy and they never achieve anything of consequence because of their inability of working hard towards their goals, if anything if I had to choose which one of the two was better being hard working will win hands down since at least the one that is working hard is making progress towards his goal while the smart person is sitting just thinking and doing absolutely nothing to get to his goal.