When comparing MultiMarkdown Composer vs Quiver, the Slant community recommends MultiMarkdown Composer for most people. In the question“What are the best Markdown editors for OS X?” MultiMarkdown Composer is ranked 12th while Quiver is ranked 16th. The most important reason people chose MultiMarkdown Composer is:
Not many popular Markdown editors support MultiMarkdown syntax.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Multimarkdown support
Not many popular Markdown editors support MultiMarkdown syntax.
Pro Multiple export options
You can export to HTML, PDF, LaTeX, RTF, OpenOffice, Microsoft Word, ePub, OPML.
Pro Table of Contents support
Generates a table of contents based on the headers in the Markdown file being worked on.
Pro Support for elastic tabstops
Elastic tabstops are used to align text automatically during writing. When there's a change in the text, MultiMarkdown Composer automatically aligns all lines both on the beginning and end of them.
Pro CriticMarkup support

Pro Optional synchronized scrolling
Hold a key down and get synchronized scrolling.
Pro Fast syntax highlighting
Pro Highly customizable
Pro Counts words, characters, lines
Pro Can show invisible characters
Pro Has more features than just a simple Markdown editor
Quiver is a notebook and note-taking app akin to Evernote which happens to also be able to edit Markdown files. As such, it has a lot of useful features such as: image support, file attachments, web content support and more.
Pro Supports code highlighting
Has syntax highlighting for more than 120 programming languages.
Pro Notes can be linked to each-other
Quiver notes have unique links that can be copied and pasted into other notes to gain quick access between them.
Pro Live preview
Quiver has live preview for both Markdown and LaTeX. This helps users to better understand the way they are formatting their files.
Pro Cloud syncing
Dropbox, iCloud Drive, Google Drive, or any other file-based cloud services.

Pro Supports vi keybindings
For people used to vi keybindings, Quiver can be set up to work with them.
Pro Combination of different types of writing in one note
The most outstanding thing for me. Use HTML line breaks while writing MD text.
Also, unlike most hybrid editors like Bear, it supports instant image sizing and respective preview.
Cons

Con Table of contents gets out of sync sometimes
If you keep the auto-generated table of contents open while you work it gets out of sync, meaning items in the table of contents (at the end) disappear until you restart the program.
Con The way the preview shows images is inconsistent
The preview is a bit inconsistent with images. Sometimes it shows the image correctly, sometimes it shows a blue question mark.
Con You can't edit specific files, they must be in your notebook
Con No iOS apps for editing, only a viewer available
I'd LOVE to edit and create quiver notes on my iPad!
Con The line in focus shows a border around it which is distracting
The line in focus in the editor shows a rounded rectangular border around it, which is unappealing and distracting.
Con Much more than a simple Markdown editor
Since it's more like a note-taking app (and a note-taking app built for developers) than a Markdown editor, it may be a little excessive to use it only for its Markdown editing features.
