I can believe that a tool's design would result in it being difficult to use, if the tool had been designed incompetently ("Korean chopsticks are kind of flat; and that design makes them difficult to use"). But the way you word it here, it sounds like difficulty-to-use was intentionally designed into the chopsticks, and I find that very difficult to believe. Why would they do that? :D

The first one is gramatically correct. The second one would also work in conversation.