Comment by eonil

What you have to deal with;

* Xcode = iOS bugs + UIKit bugs

* Xamarin = iOS bugs + UIKit bugs + different runtime, language, memory model abstractions + .NET bugs + P/Invoke bugs & overheads + GC inter-op bugs & overheads + C# bugs + slow followup of platform updates

* Xamarin Forms = iOS bugs + UIKit bugs + different runtime, language, memory model abstractions + .NET bugs + P/Invoke bugs & overheads + GC inter-op bugs & overheads + C# bugs + slow followup of platform updates + extra UI abstraction layers + lack of fine level controls & features