This is an intriguing question for me. I am a web developer by profession. I am convinced that I need to learn at least one mobile platform to keep up with the times.

I have an old Android flagship phone. I never considered iPhones because they are too expensive in our country. But the majority opinion I see in sites like HN and Reddit lean towards iOS. They say that you can earn more on iOS.

I would like to develop in Android because that is the phone that I have. But I am also enticed by the monetary advantages that developing in iOS brings.

I already have a macbook. Is that enough to develop in iOS? Or do I need an iPhone to truly test apps?

I've always thought the contrary — native apps are here for some time, until they get replaced with HTML5 apps almost completely, so no need to bother.

Well nothing beats testing something out better than on the physical device it's designed for.

Java is much more ubiquitous than Swift/ObjectiveC. I don't know that I would consider a career writing Java "better" though.

Going from iOS to Android is easier than going from Android to iOS. Learn iOS first.

Personally I do Windows, Android and iOS. Xamarin allows me to use and share C# code for all 3.

I'm a web dev working with C# and like other people in this thread I've felt the need to learn something mobile. I looked at React Native, Ionic, and native Android, but I still haven't taken the leap into concentrating on something in particular. With the recent developments with Xamarin, I think that might be the direction I take. I really hope Xamarin can gain a lot of momentum and popularity.

Both.

I believe you will have to do both as you progress in your career.

you should develop for both platforms