Obsidian is knowledge management tool, you can think of it like a personal wiki. So it gives you some different types of elements that you can place inside the Canvas, e.g. notes, PDFs, videos, audio, and even iframe web pages.

For example you can embed embed Markdown notes inside a Canvas, and embed a Canvas inside a Markdown note.

It's in a completely different product space, so there's that to differentiate them as a start.

Are you familiar with FigJams?

Still very different. Obsidian Canvas is about spatially organizing your already-existing knowledge base in Obsidian. Figjam is more like virtual whiteboarding. Big big fan of both Obsidian and Figma/Figjam, they don't really compete here though.

They’re building up to these features from plain text.

Similarly, right now they’re discussing how to contain a node-based database in human-readable markdown comments.