When comparing React Native vs MonoDevelop, the Slant community recommends MonoDevelop for most people. In the question“What are the best tools for making a cross-platform application?” MonoDevelop is ranked 6th while React Native is ranked 10th. The most important reason people chose MonoDevelop is:
MonoDevelop is free to download and use.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Allows you to develop native apps
React Native allows you to create native apps by generating native views with JavaScript instead of using a web wrapper.
Pro Large, supportive community
Despite being such a young framework (early 2015), the support for React Native grew quickly. There is a forum, active tag on Stackoverflow and many other ways to get help from the community.

Pro Backed by Facebook
Facebook writes their mobile apps in React Native so the code base gets pretty thoroughly used in some highly demanding scenarios.
Pro More predictable control of the state
The one way data flow, makes it more predictable and easy to control.
Pro Free
MonoDevelop is free to download and use.
Pro Starting up this program doesn't take as long as starting Visual Studio windows 98
Cons
Con If core team doesn't use a certain feature, it's not developed
Whenever there's functionality you need that they don't use in their apps, it's not going to get developed by them, even if it's obvious it should be in the core. They always say to either submit a PR or create a separate module.
Con Steep learning curve
React Native is not the most beginner-friendly framework for creating mobile apps with JavaScript. It requires that the developer know React, which is known to have a steep learning curve.
Con Many existing JS libraries are not usable on React Native; not exactly a 1-to-1 experience to writing React either
Example: Library that provides a full calendar with agenda view.
In the end it's much easier to develop in actual JavaScript with a solution such as Ionic, especially if your app needs to work well on the desktop.
Con React native only supports react which is getting old
React native is only based on react which is getting old. An old tech developer can't take much breaking changes so it gets more patchs. There is a limit, and react is too verbose and complex. better alternatives available today.
Con No longer supported (deprecated since 2018)
Starting with version 4.x, Xamarin rebranded MonoDevelop as Xamarin Studio, but only for the Windows version of the IDE.
Stable release
7.6.9.22 / September 21, 2018
Con Bad formatting
MonoDevelop doesn't offer much in terms of autocompletion and code formatting. Most of the time the automatic formatting that MonoDevelop does is annoying and not really compliant with C# guidelines.
Con The MonoDevelop version that ships with Unity is several versions behind
The version of MonoDevelop that ships with Unity is several versions behind the main MonoDevelop branch. It also gets updated very rarely so any annoying bugs that it may have take a lot of time to get fixed.
