Why choose Xamarin?
One of the major advantages of using Xamarin is the shared codebase when building apps for multiple platforms. It greatly shortens the time you need to devote to creating the apps themselves – with the shared codebase you do not have to develop each application version from scratch. Besides, there is much less effort needed to deal with the fixing and debugging of the applications built (less code means reduced scope for errors).
Lower costs and faster implementation
Another benefit that you simply cannot underestimate is the cost. Normally, when building an app for all mobile platforms, you need to use three different programming languages, Java for Android, Objective-C for iOS and C# for Windows Phone. With three languages, there is a great chance you are going to need to hire more developers to get the job done, which will impact your budget. With Xamarin, you can create apps written in just one language, C# and re-use up to 80% of the code between the platforms. It greatly reduces the amount of work that needs to be done and the number of people involved in the project. All this contributes to easier and cheaper maintenance, lower development costs as well as lower expenses related to the introduction of the new features and modifications in the future.
Importantly, using Xamarin allows you to keep native UI and SDK features which are specific to each of the platforms. This creates a better and more fluid UX, since the end-users are exposed to the interface they are already familiar with. Furthermore, with access to .NET classes, Android-specific classes and iOS-specific classes, the apps can share the same core logic, while at the same time embracing unique features distinct to each of the platforms.
Xamarin seems to be a viable option, when you already have a Windows Phone app, or when you are planning to build one. Since you already have to write the business logic in C# and .NET, why not re-use it for other projects thus saving time, effort and resources you would need for developing all the other apps from scratch.