Once you're sure you're buying an iPad and now, the next step is to decide which iPad you're going to get. And right now it's a tougher decision than ever. The new iPad Air and Retina iPad mini are identical in every way but screen size, 7.9- vs. 9.7-inches the only differentiator. If money is incredibly tight, though the old iPad 4 is a bit cheaper, and the old iPad mini, a bit cheaper still. No matter which one you choose, however, you'll be paying hundreds of dollars. Either a few, or a lot. So do you go with big or small, old or new, cost or value? Which iPad should you get?