Thanks a lot. I am not really comparing which one is better, not at all since both are completely different and just happened they are the two most popular OS on mobile. I am just wondering how is the ecosystem to have a better in sight. Anyway thank you again!

I want to follow up about "old device", can you specifically suggest a device just to have an idea. Thanks

I agree about the difficulty answering the "how to learn". I am looking for a beginner iOS tutorial to follow but at the same time using the standard approach and architecture so I won't repeat my mistake when I was a beginner which is developing an app with whatever works and not spending time to consider a good design for good maintainability. I want to know which architecture is usually being use which can be consider as good practice. I am curious if dependency injection framework is also a thing in iOS development, I will be starting by next week probably thus preparing to know those stuff ahead.