• Javascripts is the most populated language in the world.
• Easy to learn & deployed production
• Fast development
• Strong community
• Completed Documents
• Native performance with lower RAM used.
• Easy to handle native issues by using native code like Java / Objective C
• Powered by Facebook.

While with Ionic it is possible to make mobile applications with only web technologies, Flutter is more performant and is easy to use if you are willing to learn Dart, which is a fun language. Plus, it has awesome documentation and, while its ecosystem isn't near as big as JavaScript's is, it has a good package manager called Pub and its packages are generally high quality.

I've done some Hybrid Mobile apps with both technologies Apache Cordova and React Native and described my experience in my blog.

In a few words, I would suggest to use each technology in accordance what what is your current code base and what do you want to achieve.

React Native is a great option if you need that extra edge in performance with multi-threading and native UI rendering. Or you already have a web app based on React which you want to port to mobile.

On the other hand, if you have an existing web application code and you want to reuse some or all, including the ability to use web third-party libraries, then Cordova is the best option.