C# better than java, maybe but than Kotlin ? That's a very subjective opinion.

Apps written in Xamarin and kotlin work very differently :

-with Xamarin you have to add the Xamarin runtine and depend on its integration. This brings several downsides : http://www.slideshare.net/KonstantinLoginov/we-are-ditching-...

-Kotlin outputs bytecode, so from the outside, it is just the same as any android app written in java. The output is a standard android app with one more library (the standard kotlin lib with all its base methods)

Probably because IntelliJ is a superior IDE, Kotlin is a better language than C# and Xamarin apps look and perform like ass.

I like both, but why do you consider Kotlin better than C#?

I also don't get your point about how lame Xamarin apps look. Xamarin apps use native layout components (could be wrapped with lowest common denominator abstractions in case of Xamarin.Forms, but it's optional), so they're 100% capable of looking the same way your native app would.

iOS and Android UX guides have completely different approaches to the logic of user interaction. AFAIK, Xamarin does not allow to have different layouts generated from shared code. So, even that components are native, their placement is alien.

> Xamarin does not allow to have different layouts generated from shared code

That's true, but noone says or recommends that all the code is shared. Typical Xamarin architecture and good practice assumes sharing the business (or domain) layer, and coding the views separately. In terms of reusability it's still superior in comparison to writing both versions natively. Obviously the level of reuse you can achieve that way very much depends on the nature of the application.