When comparing Xamarin vs Codename One, the Slant community recommends Xamarin for most people. In the question“What are the best tools for making a cross-platform application?” Xamarin is ranked 14th while Codename One is ranked 17th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Xamarin Insights and Test Cloud increase user experience
Pro Cross-platform
Apps built with Xamarin can run natively on Android, iOS and Windows Mobile. Xamarin compiles the same C# or F# codebase to native code that runs on several platforms.
Pro Open source
The Xamarin SDK is free and open source and released under the MIT license.
Pro High performance
Pro Open source
Pro Highly customizable
By utilizing lightweight component architecture and the built in graphical designer and theming options you are able to customize a good looking app on any platform.
Pro Java 8 support
Pro Works with all IDEs
Works with NetBeans, Eclipse, IntelliJ, etc.
Pro Multi-platform development environments (via build server)
You can even use Linux desktops to build native iOS apps, no need for a Mac.
Pro Vibrant & helpful community
Pro Attractive pricing
It is possible to build production grade apps even with the free version. Pricing is decent when compared to competitors like Xamarin.