When comparing Xamarin Forms vs Codename One, the Slant community recommends Xamarin Forms for most people. In the question“What are the best systems to deliver native Android and iOS apps from one code?” Xamarin Forms is ranked 4th while Codename One is ranked 8th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Many tutorials online to start learning
Pro Supports F#
Xamarin supports F#, giving developers a functional language for building native apps on iOS, Android and Windows.
Pro Free
Microsoft bought Xamarin and made it free.
Pro Cross platform
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.