Short review of Google Pixel 4 XL I bought a few days ago.
Things that I haven't seen most reviewers talking about.
It's 90Hz, but not really.
It switches to 60Hz via various triggers. Lowering brightness below 75% in a dark room will switch it to 60. Turning on the lights and scrolling can bring it back to 90. After some testing I can't say I know exactly how it works, but it's tied to screen brightness and the light sensor. Key takeaway: it's not 90Hz all the time.
But one thing for certain: 90Hz with low brightness will give you green tint on the screen. Google couldn't really perfectly calibrate the display for 90Hz, probably. Everything is a bit greener. That's alone enough reason to not use "Force 90Hz" that's available through Developer Options.