1. Just more code – applications for Android are written in Java, which is simply a more verbose language than Objective-C or Swift. You’re bound to write more code. More often than not, having to write more code means working longer and more potential bugs.
2. Emulators are slower – even with GenyMotion, Android emulators are just slower than iOS simulators. This is just a factor that slows down the overall development.
3. Fragmentation – more devices to test against, more potential vendor-specific bugs (“Damn, this only shows up on this random Chinese phone you can only buy in Lithuania!”)
4. XML layouting – on Android, layouts are primarily written manually in XML, so WYSIWYG techniques are used less than on iOS.