PlayCanvas is like using an Unity like tooling that was developed for WebGL as only target.
BabylonJS is more high level, you can use it from either JavaScript or TypeScript, it has a playground which is more IDE like than the threejs editor, and it follows a scenegraph approach, with additional tooling for working with meshes, GUIs (early steps), animations, ... Since it is also used by the Office team, effort is being taken to make it work on top of React Native as well.
Microsoft has a YouTube channel with BabylonJS tutorials.
