When comparing Scrivener 2 vs iA Writer, the Slant community recommends iA Writer for most people. In the question“What is the best Markdown editor for OS X?” iA Writer is ranked 9th while Scrivener 2 is ranked 32nd.
Ranked in these QuestionsQuestion Ranking
Pro Built-in research management tools
Allows keeping all research material and notes of a project, including web links, pdf files, image files, multimedia, etc.
Pro Outline and Corkboard Views
Pro Multiple project templates to choose from
Pro Massively customisable export options
Pro Can tell how long it would take to read through what you've written
Pro A mode that brings focus to the sentence you're working on
Enabling Focus Mode will dim the whole text except the sentence you are currently writing on.
Pro Create whole document by including separate images/markdown docs
This is new and very awesome feature in iA Writer 4.0
Pro Markdown support
Pro Noise Free Writing Experience removes even the program bar
The Noise Free Writing Experience is one of the first approaches to create a first class distraction-free environment. The feature hides the Mac program bar when you start writing.
Pro Can export a Word document
Pro Available for all Apple devices
iA Writer is available for Mac, iPhone and iPad.
Pro Syncs using iCloud and Dropbox
iA Writer can sync documents using iCloud or Dropbox from within the editor for use across multiple devices.
Con Outdated interface
[not still true with a recent update : october 2015]