When comparing MacDown vs MWeb, 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 MWeb is ranked 18th. 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 Excellent support of LaTeX equations
Math-heavy note takers, look no further. Mweb even supports the basic LaTeX equation labeling and referencing, which you cannot find in any other markdown editor as of early 2018. Library management is another major plus.
Pro Supports publishing to popular web platforms
MWeb can publish Markdown files to various web platforms including (but not limited to) Wordpress, Metaweblog, Evernote, Blogger and Tumblr.
Pro Syntax highlighting in fenced code blocks
MWeb has syntax highlighting for some popular programming languages inside fenced code blocks.
Pro Comes with an iOS app with iCloud sync
Once you are done editing your note on your mac, it's immediately available in your iOS devices, great for checkup anytime as you go.
Pro Drag & drop or paste photos to the editor and display
Supports adding pictures to a Markdown file either through drag-and-drop or by pasting it.
Pro Small but powerful
It has file tree, can post article, can upload pictures, can render in pretty preview themes, and is small and fast.
Pro Supports both its own database and external folders
So you can have a side project stored on its database, and your current notes on external folder, with simple files, that could be share with other apps.
Pro There's a free version, Mweb lite, on Mac OS and iOS
Pro Supports publishing a static blog on FTP
Possible to manage your self-hosted static blog with your own css
.
Pro Tables
Quick insert and editing of tables.
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 Indie app, possible to be abandoned at anytime
If you like the app, please buy it to make it sustainable.
Con Price become expensive
MWeb used to cost $14.99, and could be bought half the price with promo; but version 3 now costs $20, and the developer would like to go to a subscription plan.
Con No free version
MWeb costs $20.99 and is available on the Mac App Store. There's a free trial available but it's only for 14 days which may not be enough to make a good evaluation of the software before buying.
