With the exception of Keynote, Numbers and Pages have not behaved well for me when given large documents. Numbers in particular struggled with datasets that Excel would handle very easily. I would rather use Google docs than bother with Pages / Numbers.
I'm certainly no advocate of Numbers. Pages I use for pretty demanding stuff and I've had no problems. Word has problems editing a simple letter, but it certainly may scale to very large documents better than Pages -- but if you're doing that kind of thing, I'd recommend Framemaker.
