Back when I got the first 120Hz monitor I used my old 60Hz LCD as a secondary monitor. Moving the mouse cursor across felt like it went from free and fluent to moving through molasses.
As you say, I hadn't noticed anything when I just had the 60Hz monitor.
Likewise with the resolution. I briefly maintained a dual monitor setup, one was a vertical 1080p 27 inch monitor and the other was 4k. The pixel density of the 1080p monitor was genuinely Paleolithic in comparison, so I couldn’t even use it because of how obviously I could tell. But when it was my primary monitor it never occurred to me.
wps|7 days ago