I've been working on setting my app up for all device sizes. I'm going to hard code all the frames (through my calculations) and use
CGRect frame = [[UIScreen mainScreen] bounds];
I went ahead and did your example to show you essentially how it could work with auto layout. Of course there are other ways to accomplish the same thing...
Imagine a circular button in the center of a 320x568 screen 60 points down from the top. When you take that button to a 375x667 screen 3 things are going to happen. The height and width will equally increase, AND the y-position of the button will increase (move down the screen). With constraint building, this scenario is (for the time being for what I can do) impossible.
I used 4 constraints
On iPhone 5
On iPhone 6s
There's a bit of an optical illusion created here because of the difference in screen size, but the button is both lowered and bigger on the iPhone 6s compared to the 5. That's what you were looking for.