I compare them with two versions of tea: one is green tea and the other one is black tea. It`s a matter of taste, of what you ask from an mobile operating system and how much you are willing to pay
Generally, Android is flexible, crowded with all kinds of applications, cheaper, but a little bit more unstable comparing with iOS
On the other hand, iOS is more secure, sometimes the most popular apps are exclusively launched on it and it`s more expensive
