WebVR Comparison: A-Frame vs. React-360
Note: As of 2022, React 360's repo has been archived, suggesting that Facebook is not continuing support for the project.
A-Frame is a framework for building VR worlds using declarative HTML-like components. It has a rich collection of available components from a vibrant community, and is great for creating intricate 3D scenes that can be viewed in VR. React 360 serves a different use case focused around applications that rely on user interfaces, or are event-driven in nature.
In short: If your application is driven by user interaction, and has many 2D or 3D UI elements, React 360 will provide the tools you need. If your application consists of many 3D objects, or relies on complex effects like shaders and post-processing, you'll get better support from A-Frame.