iPads Pro 2nd generation (2017) and newer feature 120 Hz display. Apple calls it ProMotion. Thanks to ProMotion, screen is refreshed 2 times faster than common LCD display. It’s not only good for Apple Pencil and artist – ProMotion (and other optimizations) reduces latency from 50 ms to 20 ms and thanks to software optimizations in iPadOS 13, it’s lowered to incredible 9 ms – but also for common user. All is more fluid and responsive and you want to touch such fast screen. iPads Pro with ProMotion technology still use classic LCD, though it’s Retina (or Liquid Retina in 3rd generation of iPads Pro) and color accuracy is market-leading. Creating a 120 Hz OLED panel with P3 color gamut and high color accuracy – not oversatured – is pretty channeling and expensive, so that’s may be reason why hi-end iPads still use classic IPS LCD display.
Apple already uses OLED Super Retina displays for most iPhones since iPhone X (for example, iPhone XR still uses LCD), but refresh rate is still 60 Hz. iPhones are not mean to edit photos in Photoshop with Apple Pencil, but high refresh rate could make using an iPhone more joy and also it’s better for human eyes. And also, it would be a big marketing advantage over competition from Android world.
There are already Android smartphones with 90 Hz refresh rate, like Google Pixel 4, or even 120 Hz Asus ROG phone. iPhone is still set at 60 Hz refresh rate.
This may change in 2020. The Chinese version of a Digitimes reports that 2020 iPhone will feature a 120Hz screen.
OK, you may say that 120 Hz panel is just marketing, our TVs use 60 Hz panel, our computers got 60 Hz monitor, we are playing games at 60 FPS and no problem. If you own an iPad Pro with ProMotion display, you can test it how could looks if your iPad Pro was not using ProMotion, just follow THIS GUIDE how to easily limit FPS to 60 FPS/Hz.