People say Office is better, because of all the features.
I say iWork is better, because it doesn't have the bloatware that Office does.
Instead, it focuses on getting you done. Keynote is miles beyond Powerpoint. Pages is faster, and easier, than Word. Numbers is the only part of iWork that really lags noticeably behind its Office counterpart.
My solution is both. If I need to collaborate, then I open it in Office. If not, iWork (or Scrivener) it is! Of course, that solution isn't always the easiest, nor is it the cheapest, which is probably its biggest downfall.