When comparing MacDown vs Caret, 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 Caret is ranked 25th. 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.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

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 Good auto-completion
MacDown has a good built-in auto-completion engine for Markdown symbols.

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 Linking between pages
Unlike a few other editors, MacDown lets you link between markdown pages.
Pro Tool bar with most used markdown shortcuts
This is especially useful for Markdown novices
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 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.
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.
