When comparing MacPorts vs MacDown, the Slant community recommends MacDown for most people. In the question“What are the best developer tools for Mac OSX?” MacDown is ranked 4th while MacPorts is ranked 20th. 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 Provides a consistent experience across OS X versions
MacPorts eschews Apple-supplied libraries and links sources against its own making sure that the experience is the same regardless of what OS X version is used.
Pro Easy to use
Detailed instructions on the homepage are easy to follow. Official GUI app is also available
Pro Generally very up to date
MacPorts generally gets new software soon after it's available. This way users will not have to worry if their software is up to date.
Pro Nice variants system
MacPorts has a variants system that allows customizing builds with author provided options.
Pro Has many more packages than its competitors
As of this writing, 20K packages. 3 to 5x more than other current package managers.
Pro Requires SUDO to install apps
No need to worry if some rogue app will change your binaries or configuration.
Pro Download libraries instead of relying on Apple's caprices
Considering just how often Apple breaks things, any reduplication of of Apple-supplied libraries with the canonical sources is an asset.
Pro Fast
Written in Tcl & C, it's generally significantly faster than the competition. Tcl is also quite readable and comparable to Ruby, so it's also friendly to newcomers.
Pro Supports older Mac operating systems
Homebrew dropped support for old Macs. MacPorts still supports them.
Pro MacPorts is a native application: C + TCL
No need to install Ruby, or any other programming language.
Pro More packages than competition
Pro Apple Silicon Ready
With Apple moving over to its own silicon, macports has been ready for the move to ARM since 2.6.4
Pro Initially started and developed by Apple employees and supported by Apple itself
Reading the story behind MacPorts, it is the only one that was developed by Apple by an Apple employee. In fact it is the same person that was responsible for creating the FreeBSD port system.
Pro Great support for older systems
Pro Most of the available packages work
For example, trying to install Finch using Pkgsrc doesn't work, while installing it using MacPorts works perfectly. Finch isn't even on Homebrew's radar.

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
Cons
Con New Packages and Updates take time
Macports isn't the first choice for developers producing new packages or binaries for macOS. Nor is it the fastest in getting updates. But in general, it usually is one of the most up to date and will be updated eventually. Some would see this as a con in comparison to Homebrew.
Con Bad at limiting dependencies
MacPorts has a habit of pulling very specific versions of dependencies for each package. It downloads different version of already existing dependencies even in cases where the existing dependency version would have worked seamlessly.
Con Downloads unneeded libraries duplicating functionality already provided by Apple's libraries
As MacPorts eschews Apple-supplied libraries and links sources against its own a large duplication of functionality across MacPorts and Apple libraries can be found.

Con Requires root permissions (sudo) for installation of packages
A really good security feature, but some see it as a con.
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.
