As you can see, there is no one right answer. Every writer is different and has different needs.
Some people swear by Scrivener. Others swear at it. It's fairly good as an organizational tool, but less good in creating the final MS. I have no trouble with organization; after decades of practice I can keep very complex structures in my head. I only use a separate file to keep track of names and ages and such for my characters as I can't always mentally keep track of those details.
Some people used an office database program or spreadsheet to keep track of the information Scrivener can keep track of. They do that usually because they already use those tools and find them easy to adapt to their writing needs.
I use Word 2002, an OEM copy I bought for $20 a dozen years ago. It does what I want. I use few of its advanced features, so am not interested in getting a later copy. If you want free, LibreOffice is a good choice, marginally better than the other versions of OpenOffice.
http://www.libreoffice.org/
I do somewhat as Roxxsmom does. I set up my MSs so they closely match the way they'll be published. For a 6" x 9" page, single-spaced, etc. This lets me see when my paragraphs are too long (by my standards), dialogue too confusing, etc. I have a header with my title & page number on odd (left side) pages, name & page number on even (right side) pages.
When the book is done I can self-publish it on CreateSpace (after adjusting for Word's crude type-setting facilities). For my later books, for which I'm seeking an agent, I still print out a CS copy. For I've found that copy-editing a printed book, rather than a printed MS, helps me find problems I can't see otherwise.
But that's me. Your needs will inevitably vary & you likely will have to try several tools before you settle on ones which suit your needs.