When comparing Texts 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 11th while Texts is ranked 14th.
Ranked in these QuestionsQuestion Ranking
Pro Immediate Markdown rendering and preview
Texts immediately renders the formatted Markdown as you are typing it inside the text box. It's quite similar to a WYSIWYG editor.
Pro Supports multiple Markdown dialects
Unfortunately, this is a global setting for save (it can open any dialect)
Pro Imports and exports many formats
HTML, Word, TeX, PDF, ePUB, OPML.
Pro Works on Mac OS X and Windows
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 Available for all Apple devices
iA Writer is available for Mac, iPhone and iPad.
Pro Can export a Word document
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 Overwrites standard Markdown
Editing a preexisting Markdown document overwrites standard markup in it (for example, interpreting headings marked with leading "#"s and rewriting them with a trailing underscore line), adds extra blank lines between all paragraphs, and adds extra spaces at the head of unordered-list items.
Con Spell checking is not activated by default
There's a built-in spell checker which is not activated by default and is quite hidden.
Con Limited choice of built-in themes
You can download the CSS for these themes and create your own, but would be nice to have more flavors (e.g. GitHub)
Con No word count in older versions
Word count is present in Texts 0.21, at least.