When comparing MacPorts vs Mou, the Slant community recommends Mou for most people. In the question“What are the best developer tools for Mac OSX?” Mou is ranked 13th while MacPorts is ranked 20th. The most important reason people chose Mou is:
Mou has word auto-completion (accessed via 'esc') for English words, text transformation such as conversions to uppercase, blockquote or an h1 heading, HTML entities (such as <’s, &’s and spaces) that can be added anywhere in the text and customizable keyboard shortcuts for everything allowing for efficient use of the software's capabilities.
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 Advanced text editing
Mou has word auto-completion (accessed via 'esc') for English words, text transformation such as conversions to uppercase, blockquote or an h1 heading, HTML entities (such as <’s, &’s and spaces) that can be added anywhere in the text and customizable keyboard shortcuts for everything allowing for efficient use of the software's capabilities.
Pro Full syntax highlighting
Mou provides full syntax highlighting for Markdown. The highlighting can be customized manually or by applying a predefined theme.
Pro Has real-time split-screen preview
Mou is split into two columns. It displays raw Markdown on the left and formatted text on the right. Text on the right will update in near real-time as raw Markdown is written.
Pro Powerful search
Mou can do incremental ("find as you type") pattern matching search. For example, it can find all words that have x as the third letter followed by at least 4 more letters and a line break.
Pro Free beta versions
Mou is available as a free download up until the release of 1.0.
Pro Customizable
The whole editor can be customized using different color schemes and users can create own variations by editing CSS.
Pro Support for CJK characters
Mou supports CJK characters for writing Markdown in Chinese, Japanese or Korean.
Pro Export as HTML or PDF
Markdown can be exported as an HTML or a PDF file. Each export can also be styled by a custom CSS.
Pro Customizable keyboard shortcuts
Mou has keyboard shortcuts for all text manipulation actions allowing for highly efficient use of the software. These shortcuts can also be manually edited to better fit each individual workflow.
Pro Includes optional typewriter keypress sounds
The app includes optional atmospheric typewriter sounds that are triggered with each keypress. These can be enabled in the settings.
Pro Scriptogr.am & Tumblr integration via Dropbox
Mou allows writing and publishing to blogs from within the editor.
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 No longer maintained
The latest version was released in 2014, version 1.0 was announced for 2015 but was never released. The app is not compatible with macOS Sierra.
Con Only free until 1.0 release
Once 1.0 is released (still unreleased as of May 2017, release was planned for August 2015), Mou will cost $30. It can currently be pre-ordered for half the price.
Con Text is hard to read on a big screen in full-screen mode
On big screens legibility is pretty bad when entering full-screen mode because the text is not columned nor centered. On smaller screens though, legibility is quite good even on full-screen.
Con Doesn't work as well with non-monospaced fonts
When using a non-monospaced font, the text jiggles around. It can be very annoying since users may not always want to write with a monospaced font.
Con Switching live preview on/off changes the width of text area
Con v1.0 was promised to Indiegogo founders more than a year ago
Safe to say this is dead software at this point.
