AutoLayout
will make it easier to adjust your UI for both screen size, but even with the old UIViewAutoresizing
you will be able to get everything working.
I would suggest that you do not use 2 storyboards or NIB for that mater, because if a some point an other screen size is introduced you need to create a third storyboard/NIBs.
You can even use the UIViewAutoresizing
in NIB and in code.
Just set the autoresizing mask correct to grow/shrink with the screen size and you will be good to go.