Lisa Eadicicco on the obvious:
Although there are plenty of differences between Android and the iPhone, there’s one main discrepancy that stands out the most — with Android you get choice, while the iPhone is one uniform platform.
There are thousands of Android devices in the world. Companies from Samsung to LG to HTC and even Amazon make phones and tablets that run on some version of Android… It also means that there’s a slight learning curve with each Android device since they all work differently and have software that differs from one phone to the next.
Unity, simplicity, and security, vs. confusion, complexity, and unfixed security flaws. Easy choice.