Look at it this way. The iPad Mini is a small iPad 2. It's speed, graphics, everything is slightly updated tech from two years ago. The iPad Mini Retina is essentially an iPAD Air with a smaller screen. For $100 you are getting the most up to date iPad available. Buying older devices saves you up front, now. Buying the newest device will give you an extra year or more of staying current with updates and being able to use the newest apps. Whether you should buy old or new is mostly a matter of how you intend to upgrade. If you want a device for the next year, and maybe one after that, the older iPad is good. If you want to get the longest possible time before you upgrade again, then the newest will save you money (assuming you can resist upgrading whenever you see the newer, shinier models

). Anyway, that's the way I do it. I buy the best model I can afford at the time. I admit that with iPads and iPhones I also upgrade before I have to, but the older models go to my relatives so long term usability is still important to me. And I have a weakness for "ooo, new, shiny" things.