I use Office on the Mac and iOS. They are compatible but not comparable. iOS has a stripped down set of features so they are fine for basic tasks such as creating documents, spreadsheets, presentations but for more advanced features you need to migrate the document to a Mac. I view the iOS versions as excellent portable tools that can do a lot of what I need and are far more convenient to use on the go but the final editing needs to be done on a Mac or PC. For example, I use mail merge and linked files to create final reports; something you can't do with the iOS versions. I can create the base documents on the iPad and then integrate them on my Mac. Similarly, in iOS, embedded videos are not possible in PowerPoint and I've had issues with complex formatting or odd fonts.
That said, Office on the iPad is a very useful tool. I've never really transitioned to iWorks, despite being a long time user of its predecessors on the Apple ][ and liking Keynote; since all of my clients use MS Office and thus I need to produce documents using them to ensure compatibility.