When comparing WikidPad vs Zettlr, the Slant community recommends WikidPad for most people. In the question“What is the best single-user wiki?” WikidPad is ranked 8th while Zettlr is ranked 16th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Free
Pro No remote server needed, or wanted
Pro Export to HTML built in
Export to HTML built in and can work with Dropbox.
Pro Data is stored in standard Text files
Data can be viewed, edited, searched, exported easily, and can work with Git.
Pro Instant cross-referencing methods
On the fly WikiWord linking, as you type.
Pro Quick, auto-saving, and auto-organizing
Auto-organizing with URL and file linking, and instant new-page methods.
Pro Focuses on writers
While many Markdown editors don't offer specific support for a certain type of workflow, or offer features for scientific workflows only, Zettlr offers features that help the writing process of journalists or researchers in the arts and humanities. It's a lot more text-focused than most editors.
Pro Citation support
While it supports a diverse range of syntax (chart, easy image insert, etc.) found in other editors, the great citation support made it possible to write real articles. Citation from Zotero and Mendeley can be inserted easily which is a huge plus.
Pro Almost perfect
This is the best option, still not perfect, there are some bugs like creating / editing tables and resizing images, but the PROS destroy the CONS, easy quotes, WYSIWYM , attachments tab (supports attaching and opening links to any file), table of contents, TAGs, easy hyperlink between files (same as citations), export to many formats (like Word, HTML5, PDF)...
Pro Renders math in-place through KaTex
Cons
Con No MarkDown support
Con Obtrusive, like someone WITH CAPS LOCK ON
Too loud, too much going on, and definitely an in-your-face sort of feeling.