I use both Pages and Microsoft Word.
The one brilliant feature in Pages is that you can keep the same document open on two Macs or iOS devices and it manages the sync through iCloud without hiccups. If it's a document I would like to read or edit on my iPhone, I keep it in Pages.
I do like MS Word too. The notebook layout in Word 2011 for Mac is quite nice, and I've found it valuable over the years to learn the advanced features available in Word. But, I've got to take care not to open the same Word document simultaneously on two Macs, and I still don't trust the 3rd party editors on iOS with my Word documents.
So, in short, Pages for portability and MS Word for functionality 🙂