Both tools are excellent for one person taking notes. The gap only shows up when a team shares the same knowledge base. Short version: Notion scales on collaboration and access control but strains on performance and lock-in; Obsidian scales on speed, ownership, and Git-friendliness but has no native multiplayer and pushes concurrency problems onto your sync layer. Which pain you'd rather manage is the real decision.
I've run engineering docs on both — Notion for a ~30-person product org, Obsidian vaults synced through Git for smaller, more infra-heavy teams. The failure modes are predictable once you know where to look.
What actually differs between them?
The core architectural split drives everything else: Notion is a cloud database with a document UI on top; Obsidian is a local Markdown editor over plain files. Every scaling tradeoff below descends from that one fact.
Dimension
