When comparing Byword 2 vs Caret, the Slant community recommends Byword 2 for most people. In the question“What are the best Markdown editors for OS X?” Byword 2 is ranked 2nd while Caret is ranked 25th. The most important reason people chose Byword 2 is:
Byword de-emphasizes the syntax itself while emphasizing its effects. It appropriately adds style, like italic and bold, to text that's designated by markdown and dims the syntax so it does not get in the way of comprehension. Additionally, there are commonly used hotkeys (⌘b, ⌘i, etc) that can be used to apply style without having to know the syntax or having to type it out each time.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Great Markdown support without being intrusive
Byword de-emphasizes the syntax itself while emphasizing its effects. It appropriately adds style, like italic and bold, to text that's designated by markdown and dims the syntax so it does not get in the way of comprehension. Additionally, there are commonly used hotkeys (⌘b, ⌘i, etc) that can be used to apply style without having to know the syntax or having to type it out each time.
Pro Available for all Apple devices
Byword is available on a Mac, an iPhone and iPad.
Pro Extremely simple
Byword is as simple as Markdown editors can get. Even though Markdown itself is not hard, Byword offers assistance to make it even easier with very little configuration required.
The UI is minimalistic and un-intrusive, the syntax auto-completion is excellent, and there are multiple small but helpful features that make writing Markdown with Byword a breeze.
Pro Syncs using iCloud and Dropbox
Documents can be synced using iCloud or Dropbox from within the editor for use across all devices.
Pro Direct publishing to web platforms
Byword allows users to publish their markdown files directly to web platforms such as Wordpress, Tumblr, Blogger and even Evernote.
Pro Word count support
Has a built-in word counter.
Pro Multiple export options
You can export to HTML, PDF, RTF.
Pro A dark theme is available
For people who enjoy working during the night, there's a dark theme available that reduces strain on the eyes.
Pro Includes features that speed up writing
For example, while authoring a bulleted list hitting return automatically prepares a new bulleted line.
Pro Live update support
Byword has a "Preview Markdown" option where it does exactly what it promises. It immediately compiles and displays the rendered Markdown file, making it easy for the user to understand how they are actually formatting their document.
Pro Supports Multimarkdown
Byword supports all the table types in Multimarkdown including table captions. MathJax support is added via metadata at the beginning of file was well as support for various diagrams. Table of Contents is also supported.

Pro Supports iCloud Drive and Handoff
One of the few (well, Ok, only for far) that has been updated for Yosemite features. Jan 2015.
Pro Updated frequently
Byword gets frequent updates which add new features or fix existing bugs.
Pro Single-pane hybrid interface
The single pane formats your MD as you write it but retains the markup so you can see what's going on.
Pro Has a heading navigator
Hit ⌘ G to see document titles in a hierarchical view, type and use the arrows to navigate.
Pro Has a file manager
Hit ⌘ T to browse current folder, navigate the file system and manage your files and folders, type to search, right click to create / move / rename / delete items.
Pro Supports multiple cursors / selections
Make ten changes at the same time, not one change ten times - lets you edit multiple lines at once, perform quick and selective find and replace, etc.
Pro Supports context commands
Hit "Enter" to fix spelling, convert list to ordered/unordered/task, convert reference link to inline, jump to reference link definition, jump to footnote definition, visit links, etc.
Pro Supports auto-completions
Auto-completion for paths of links and images, keywords in fenced code blocks, emoji, etc.
Pro Offers inline preview for LaTeX math expressions
Renders LaTeX math expressions as soon as you have finished writing them.
Pro Supports "select more" / "select less" commands
Hit ⌥ ↑ to extend the current selection to the next biggest element and ⌥ ↓ to shrink the selection.
Cons
Con No support for code blocks
I need my markdown editor to support code blocks like
def foo(bar, baz):
qux()
This one does not.
Con Publishing requires additional in-app purchase
The feature to publish Markdown files to web services costs an additional $5 of in-app purchase.
Con Expensive
Con Limited customizability
One of the things that makes Byword so easy to use is the fact that it needs very little setup and option-tweaking. However, that severely limits the ability to customize the editor itself. For example, there are only two themes available, a light one and a dark one.
Con Not free
No longer free, try and buy
Con The shortcuts don't toggle formatting
Pressing cmd+B, for example, will begin a bold segment of text, but pressing it again doesn't end that bold segment, it retroactively turns the boldness off. This interrupts writing flow tremendously.
