There is a legendary story about how Steve Jobs, upon his return to Apple, drastically cut-down the number of models that they offer. How on earth have they forgotten that lesson? Trying to figure out the differences between the 9.7" iPad and iPad pro is not easy, and regardless, it makes it harder to buy.
http://www.apple.com/ipad/compare/ to compare current models. iPad Pro 9.7 has better processor, better screen, better camera, is slightly thinner and lighter and works with Apple Pencil and Keyboard accessories. There are now just four options: big Pro, little Pro, iPad, and mini.
With the larger iPads do some people get smaller space, even though larger display probably means more resources/larger resolution media will need to be stored on the device.
Spitballing but it's quite a few options.