Substantially more Android phones are sold than are iPhones (about 5:1 in 2012). However, iPhone users do much more shopping, browsing, and app-downloading. So, what gives? This Harvard Business Review article, by Michael Schrage, discusses it. The key point is:

Designing a great device is not the same as designing a great user experience. Designing a great user experience is not the same as designing greater engagement. While it’s completely understandable why designers, product managers and marketers might conflate them, reality suggests that a great user experience doesn’t necessarily generate engagement any more than meaningful engagement inherently assures a great user experience with Views For Cash.

Engagement is really the value we get from our user experience. While some of that is obviously subjective, there are certain trends, designs, and products that tend to be more universally engaging. In UX, we need to think about the difference between actively driving that engagement and passively allowing/supporting it, and then apply that to our content and design.