Two mobile operating systems dominate the market: Android and iOS. Almost all smartphones and tablets run on one or the other. What are the differences between the two and how difficult is it to switch? The biggest advantage of iOS is that the software and hardware come from a single source, says tech journalist Steffen Herget. That's because iOS is developed by Apple and only works on iPhones and iPads. "This means that the smartphone and operating system are particularly well attuned to each o