What's the difference between the Night Shift feature in iOS 9.3 and the True Tone display on the iPad Pro 9.7"?
True Tone makes subtle changes to the color temperature to blend with the ambient lighting.
Night shift cuts the value of blue in the image to counteract the body's physiological response to blue light that makes it difficult to fall asleep after a period of viewing a computer screen.
Ture Tone's effect is subtle, and you probably won't notice it in action unless you turn it off and see the sudden change. It does, however, make viewing the screen under different lighting conditions easier on the eyes, in my opinion.
With night shift on, the screen has a definite yellow tinge which will be very apparent. This is intentional. For those of us who use the iPad to read or answer emails before going to bed, the bluish light of an LCD screen supposedly interferes with the transition into sleep. Myself, I rarely have trouble falling asleep, especially at my desk.