I prefer rive.app, it is a lot lighter and easier to work with imo, plus, it has a great editor
Why would rive website use video instead of their binary format and performant js?
Mostly to show projects on-device/being interacted with. We also designed this version of the site back before we had responsive layouts, dynamic text, data binding, etc. We will eventually update it to be designed entirely in Rive, but we're first prioritizing launching features like Libraries, Scripting, and a better way to handle Accessibility features.