I use a 4K 32'' Asus ProArt monitor and didn't notice any difference between my M2 Pro and my M4 Pro (on Sequoia). I will admit my eyesight is not the best anymore but I think I would notice given I'm a bit allergic to blurry monitors.

Anyway I will run the diagnostic commands and see what I get.

I use a 4K 45" Aorus (Gigabyte) on M4 and M2 Pro — also eyesight/age...

Both will run at 144Hz, but the M4 will occassionally flicker if you're close to limits on dual-screens. I set to 120Hz and don't notice any difference.

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My M4 complaint is that I can no longer update my OS with a USB Installer offline. My M3 (and lower) will, using the same Sequoia media.