Your 12 Pro looks way more correct in white point than your X. Your X looks too cool and has a blueish tint to it.My second replacement;
iPhone X on the left / iPhone 12 pro on the right.
edit: True Tone off on both and nightshift is also off; max brightness.
Looking at it straight on I can see a slight difference:
View attachment 984839
Viewing at an angle:
View attachment 984840
Considering keeping it but in two minds.
As someone that lives in a house with correctly calibrated monitors and OLED TVs for years now, I can assure you that A LOT of people are way too used to the (incorrect) white balance profiles of countless consumer electronic products and are used to what one has to describe as "blue" displays.
When I got every monitor and TV in my house calibrated by a professional I thought something was wrong with my monitors since everything seemed way too warm, but they were, in fact, perfectly calibrated to D65. After a couple days of getting used to them, now every TV, monitor, or even phones I see in electronic markets look so grossly blue its not even funny. Other people don't notice it because that's what they were used to their entire lives, so a deviation from their "trusty blueish display lifestyle" entices them to think something is wrong with their product (= the "its disgustingly yellow" comments).
Lastly, the are two things I want to mention:
1. True Tone on the 12 models is way to aggressive compared to previous models, so for now I wouldn't use it. It may get fixed in a future software update.
2. The hyperbole in this thread is disgusting.