The central technical difference is no browser is going to implement DOM4.1
Google's Formal Objection briefly mentions some differences:
"In its current state, Chrome will not implement the DOM4.1 spec, and is not aware of any other browser engine that will do so. There are considerable differences between the W3C DOM 4.1 and WHATWG DOM Living Standard (including but not limited to: use of invalid Web IDL, event dispatch, shadow DOM integration, custom elements integration, ranges, and tree traversal), which is what Chrome implements."
https://github.com/w3c/dom/issues/177
Biting the hand that feeds IT
