Taking React Native in Hands, you can create a handsome amount of components but for out of the box, you need third-party tools. On the other hand, Flutter allows you to create tons of components and surprisingly all components are backed by the company itself means Flutter or Google.
So, if you are a person wants default options of components then Flutter will be your crush.
More for details, you can check this article Flutter vs React Native in 2020. In this article, the author has done enough justice with the point that where to choose these platforms?