i came to the 9.7 pro from an iPad 3. after 4 years and 3 models in between, i would characterize the quality difference as "barely noticeable"
thats not to say it isn't a fine display, and i'm sure there are measuring devices that highlight the improvements, but to the casual viewer i wouldn't say its anything to clamour over.
also, all these supposed colour space improvements, and yet the main thing people notice, be it a yellow, blue, purple or green colour cast (even with true tone disabled), are generally cited as "pickiness, acceptable manufacturing tolerances, etc..."