A comparison among Ionic 2, NativeScript and ReactScript from Feb 2017. Pros and cons of each tool is available on the page.
This is a slightly older article (Aug 2016) that compares React Native and Ionic, focusing on development process, testing, community, etc. The author doesn’t choose the better tool, but instead indicates his favorite: React Native.
This article also compares Ionic and Reatic Native, but focus more on app performance and size. The author indicates React Native as a better choice.