To make a fair comparison, we compared smartphone shots taken in a bevy of different lighting scenarios, including controlled and low lighting, and also tested flash capabilities. We didn't have all of these phones at exactly the same time, but we did make a concerted effort to control the lighting as much as possible.
You'll also notice that the size of some of the images appears different. We wanted to show you the native dimensions of the images these cameras take, and their respective dimensions as well.
The article goes into great depth, so there should be enough meat in there for you investigative types.