Each one of the new iPads has IPS LCDs but they have difference performance enhancements. The iPad Air 2 and iPad Pro have Photo Aligned LCDs for higher Contrast Ratios and the iPad Pro has a Metal Oxide TFT Backplane that increases light throughput and thus power efficiency.
Interestingly, it's the iPad mini 4 that takes home the prize of having the best display. DisplayMate says it is near textbook perfect. It performed best in every category except Contrast Ratio because Apple didn't equip it with a Photo Aligned LCD.
Among all existing Tablets of any size, the iPad mini 4 takes first place and breaks performance records in many of the most important test categories including: lowest screen Reflectance (2.0 percent), Highest Contrast Rating in High Ambient Light (225), a near perfect Log-Straight Intensity Scale and Gamma of 2.22, and the highest Absolute Color Accuracy (Average/Maximum Color Errors of 1.9 and 4.2 JNCD – tied for first place with the Microsoft Surface Pro 4). If Apple hadn’t intentionally made the display’s White Point so bluish (7,109K instead of 6,500K) then the Color Errors would have been even smaller.
DisplayMate declares the iPad mini 4 as having "the best and most accurate LCD Tablet display that we have ever tested".
Hit the link below for the full comparison and test results.