After much trial and error, my writing/publishing process is now as follows:
1. Create the ms in Word. I prefer Word because it's a fully-featured word processor, but I'm also happy to use Pages. Sometimes I bypass Word or Pages and use Scrivener instead (see next point). However, I'm used to Word so I can get on with writing without having to think about the program I'm using. I haven't reached that stage yet with Scrivener.
2. Import the ms into Scrivener, where I can easily change the order of things while maintaining a whole-project view -- see My Scrivener Dashboard. It's like a nuclear-powered version of the Outline view in Word!
3. Export the Scrivener file back to Word format. I use Word to edit the ms. For the reasons given in point #1, I find it easier for 'large-scale', ie whole document, editing than Scrivener.
4. Finally, I import the finished Word document into Vellum, which I have found to be marvellous for formatting ebooks. It's easy and quick, and the results are beautiful -- which you can prove to yourself through buying the second edition of my book about how to get the most out of education conferences!
It sounds a lot more long-winded than it is! In essence, my process is based on the principle of using what I consider to be the best tool for the job at each stage.