I've tried dozens of knowledge management tools and settled on TiddlyWiki a couple years ago. It took a lot of customization to get anywhere close as useable as Obsidian is out of the box.
Here's what I love about Obsidian:
- Local files, syncs via iCloud/Dropbox/etc makes it future proof
- Markdown with [[ ]]] bidirectional links and - [ ] checklists.
- Automatically updates all old links if you rename a file(!)
- Compatible with 1Writer on iOS
- Really nice keyboard shortcuts
- Runs as its own app (in a wrapper), but can be styled via custom CSS
- Automatically parses external URLs (don't necessarily need to use the markdown format for simple .com URLs)
- Great editing experience, e.g. auto indenting bullets
- Autocomplete for everything (tags, linked pages)
- Lots of extra nice touches like graph view and the pane system to open multiple files at once