You can add a bigger battery to most Android phones. The iPhone's back isn't removable.
With some Android phones, you can open multiple apps at once.
Several Android manufacturers layer their software over the plain version of Android, often adding their own features. On Samsung and LG phones, for example, you can open more than one app at a time and run them alongside one another. On LG phones, you can even move these apps around in separate windows, change the transparency of those windows, and resize them, as shown in the screenshot to the right.