Don't get me wrong: Coda looks like a fantastic product. It also has features that Notion doesn't have, like built-in support for charts inside the document.
If there was no Notion, I would give it a serious try.
But Notion just fits my use case better.
The biggest difference is that Code is like Google docs on steroids: the UI is structured as a collection of separate documents. Which makes perfect sense in an enterprise scenario.
Notion is hierarchical. It's just an infinitely nested collection of pages.
It makes for a different (and for me vastly superior) user experience.
But ultimately both products have free tiers so you should try them both to see which fits your use cases better.