When comparing Gingko vs iA Writer, the Slant community recommends Gingko for most people. In the question“What is the best cross-platform note-taking app?” Gingko is ranked 20th while iA Writer is ranked 52nd.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro You can customize colors
Pro Allows focusing on one piece of information at a time
Since Gingko documents are "trees", they are always organized on the go. And since everything is written in cards, it is possible to focus on one chunk of content at a time.
Pro Easy to overview
Despite the complexity of the tree structure, it's always clear where you are, and how to quickly add your thoughts.

Pro Markdown support
All formatting is done via Markdown.
Pro Non-linear
Non-linear notetaking allows you more flexibility, freedom and creativity.
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 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 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.
Cons
Con Limited free version
The free version is limited to 100 cards and 10 documents. Depending on how you use it, this might not be enough.
Con No Linux support
