I'd assume something like the conceptual difference between HTML5 canvas/video ("good") and Flash ("bad"). No plugins. Better sandboxing. Open specification not owned by some specific company. An expectation of multiple competing implementations.

Basically, it's a lot of the same stuff, but a (hopefully) better implementation, and promoted in a way that appeals to the people likely to use it. Start with an old technology. Tweak, relabel, and market under the new name.