Is video playback frame rate smoother on a ProMotion equipped iPad though? Is it a 90hz or a 120hz display?
ProMotion 120 Hz, although it will drop to 48 Hz for 24 fps video content. At 48 Hz, there won’t be any artifact - telecine judder - unlike when converting 24 fps stuff to 60 Hz.
48/24=2 so the math works.
60/24=2.5 so the the math doesn’t work which can cause issues with the video. Most won't notice those issues unless they have a trained eye but they’re there.
This video exaggerates the effect, to help in the understanding of what is 3:2 pulldown judder.
To put it simply, a regular iPad can suffer from such judder, but an iPad Pro won't. However, most people don't notice it anyway on a regular iPad, so it may be irrelevant to most mainstream consumers.
What ProMotion does NOT do is frame interpolation for movies like most 120 Hz TVs may do. It’s good that ProMotion doesn’t do this because it’s bad practice, and causes the Soap Opera Effect, which I can’t stand.
Also, I believe with static images, ProMotion can drop to as low as 24 Hz, thereby saving power.
However, for most people (including in this thread), ProMotion is about smoother web page scrolling and UI navigation and stuff like that, since it’s running at 120 Hz instead of 60 Hz. If you scroll Safari on a non-ProMotion Display beside a ProMotion display, it's easy to see that the ProMotion one is considerably smoother if you're actually looking for it. However, I don’t really care that much about that because I don’t actually read web pages while I’m scrolling. I wait until I stop scrolling before I read anything. Similarly I don't really care that much smoother swiping from the home screen to the next screen of app icons. It's nice, but not a deal breaker feature.