Ulysses vs Obsidian
Ulysses is geared mostly towards professional writers who want a clean and simple tool to create and organize their work. It's a small, Apple-exclusive app with a ton of polish.
Obsidian is mostly known for its powerful note-linking abilities. You can easily build and navigate whole knowledge bases with Obsidian. That said, it's definitely more complicated and less aesthetically pleasing than Ulysses.
Fan of note-taking apps? 🤔
Maybe Paper is what you're looking for.