Several things that are off with this study.
It doesn't say what exact models of Samsung phones it compares to the iPhone. Unless it's flagship devices vs. flagship.. err.. device, then the whole point is moot. Their little charts just say "Samsung" but Samsung makes a vastly wider range of phones than Apple, so if all (even those only considered smartphones) are compared agains the iPhone then of course Samsung's demographics are going to look a lot different.
Also, the biggest flaw I see is the "came from a previous OS" seems to just chart Samsung owners who came from iOS, but the iOS side charts iPhone users who could have come from any maker of Android phones. The only way this chart would be a relevant comparison would be just to chart only the iPhone users who came from Samsung flagship devices, or expand the 'Samsung' side to be all Android phones. Even the conclusion following the chart waxes of this, declaring what the chart shows as 'Samsung' to be "Android..."
At any rate, nothing in any of that speaks a word as to screen size preference.