It is the best because it is true. At least from what I've seen, there countless amazing engineers stuck doing really hard problems for little return, while their rather lousy counterparts razzle-dazzle the world with hand-waving; no brains necessary. If you can find an important problem that won't bore you to tears and solve it, it's definitely more important in the short term.
That said, without brilliant engineers working on hard problems and occasionally inventing really great new things, we wouldn't get far in life. So if you can forgo the fame and the riches, there is a lot of sense in working on hard/interesting problems. Someone's got to.
Personally I think picking a problem that fits your is more important than picking an outcome. The outcome won't make you happy, but the journey around the right problem will. I think.