Going from the README, the main difference is the architecture.
It creates a layer of indirection between user actions and the DOM. This has two advantages:
* For developers of Trix itself, it eases the pain of cross-browser development - as the README says, contenteditable is inconsistent across browsers.
* For developers using Trix, you get a clean API (Trix.editor) so you can edit the document programmatically without your own cross-browser development.
It creates a layer of indirection between user actions and the DOM. This has two advantages:
* For developers of Trix itself, it eases the pain of cross-browser development - as the README says, contenteditable is inconsistent across browsers.
* For developers using Trix, you get a clean API (Trix.editor) so you can edit the document programmatically without your own cross-browser development.