The screen on the new iMac is better.
24" M1 iMac
Native: 4480 x 2520
Retina: 2,240 x 1,260
PPI: 218.73 pixels per inch
24" LG UltraFine
Native: 3840 x 2160
Retina: 1920 x 1,080
PPI: 185.9 pixels per inch
To me 1920 x 1080 on 24" is OK, but it's not much space to get things done. The 2240 x 1260 is a really nice bump in usable space on the same 24" size.
Here is my 24" UltraFine setup:
View attachment 1781928
and my updated iMac setup:
View attachment 1781925