With Avada Live, you edit your content directly on the front-end. You can see your layout as you build it, and any changes you make update immediately, as you make them.
Additionally, with Avada Live, you have direct access to the Avada Global Options, as well as the Avada Page Options, on the same page, as you build. This can speed your workflow significantly.
In most other ways, the two builders are essentially the same. There are small interface and workflow differences, but they both use the same Container, Column and Element structure, and controls. The content that both builders generate is also identical, and so there is full compatibility between the two builders.