When comparing StackEdit vs MWeb, the Slant community recommends StackEdit for most people. In the question“What are the best Markdown editors for OS X?” StackEdit is ranked 4th while MWeb is ranked 13th. The most important reason people chose StackEdit is:
StackEdit works within your browser. You need internet access to connect to the website, but once it's loaded, the site does not require an internet connection - you will be able to edit and save files locally. Additionally, you can use [Fluid](http://fluidapp.com) to turn it into a native desktop application.
Ranked in these QuestionsQuestion Ranking
Pro Works online and offline
StackEdit works within your browser. You need internet access to connect to the website, but once it's loaded, the site does not require an internet connection - you will be able to edit and save files locally. Additionally, you can use Fluid to turn it into a native desktop application.
Pro No need to install additional software
StackEdit works directly from the browser, there's no need to install additional software as long as you have a web browser installed on your computer.
Pro Real-time preview
The preview shows in a collapsible pane on the right hand side.
Pro Multiple export options
Can export to .txt, .html and .pdf.
Pro Supports various Markdown flavors
Supports standard Markdown and Markdown Extra.
Pro Instant publishing
StackEdit allows pushing a document directly to a list of publishing or file storage platforms or any SSH server.
Pro Syncs via Dropbox and Drive
Files can be synchronized through Dropbox and Drive.
Pro Simple workflow
It is very easy to toggle between the preview and the editing windows. The black makes it a very focused writing environment. Of course it's possible to change that if needed.
Pro Great when in full-screen
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 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 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 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 Supports publishing a static blog on FTP
Possible to manage your self-hosted static blog with your own css
Pro There's a free version, Mweb lite, on Mac OS and iOS
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 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.
Con Cannot be accessed while being offline
Even though the editor itself works offline, you need internet access to open the website and the editor.
Con Saves files in browser's local storage
Local storage is limited and if the browser crashes the text can be lost.
Con Publishing to GitHub requires giving write access to repos
In order to publish documents to GitHub, StackEdit requires writing access to your repos, something which many people may not be comfortable with.
Con Lacks a good integrated spell checker
Uses the built-in browser spell checker which may not be as good as spell checkers other editors have. Depending on the browser, of course.
Con Indie app, possible to be abandoned at anytime
If you like the app, please buy it to make it sustainable.
Con No free version
MWeb costs $14.99 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.