When comparing MacDown vs iA Writer, the Slant community recommends MacDown for most people. In the question“What are the best Markdown editors for OS X?” MacDown is ranked 5th while iA Writer is ranked 9th. The most important reason people chose MacDown is:
MacDown is a free and open source editor influenced by [Mou](http://25.io/mou/). It's released under the MIT license.
Ranked in these QuestionsQuestion Ranking
Pro Free and open source
MacDown is a free and open source editor influenced by Mou. It's released under the MIT license.
Pro Real-time split-screen preview
MacDown's main view is split into two panels. The user types on the left and the Markdown is rendered on the fly in the right panel. This helps users to better understand the way they are formatting their document.
Pro Markdown previews can be customized with CSS
You can use a CSS file to customize the rendered output and the file preview you are working on will display the rendered Markdown with the custom CSS styling on top.
Pro Supports syntax highlighting in fenced code blocks
MacDown has syntax highlighting support for various languages when writing code in fenced code blocks.
Pro Support for GFM
Pro Ideal for day-to-day programmers' work and MarkDown novices alike
Using MacDown for the notorious README.md use case gets you going without reading any manual or requiring any configuration values. Think of it as a sort of TextEdit for MarkDown files. Thus its shortcomings - neither powerful nor versatile - turn out to be a PRO for novices trying to jump on the MarkDown bandwagon. Open its help and you'll immediately find yourself editing the MacDown's MarkDown help file, a MarkDown primer with some MacDown menus and configuration added.
Pro Good auto-completion
MacDown has a good built-in auto-completion engine for Markdown symbols.
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 Can tell how long it would take to read through what you've written
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 Markdown support
Pro Syncs using iCloud and Dropbox
iA Writer can sync documents using iCloud or Dropbox from within the editor for use across multiple devices.
Pro Create whole document by including separate images/markdown docs
This is new and very awesome feature in iA Writer 4.0.
Pro Can export a Word document
Pro Available for all Apple devices
iA Writer is available for Mac, iPhone and iPad.
Con Not very versatile
MacDown is not very powerful or versatile. It's not customizable or extendable. This is what makes it so simple, but it's not for people who want more from their tools.
Con Frequently fails to update the display and/or flat out hangs
Must often restart MacDown.
Con The Markdown preview is rather heavy on the CPU
The Markdown preview needs a lot of resources to keep rendering on-the-fly after each keystroke. A single keystroke in the editor panel may trigger up to 5 seconds of max-CPU usage.