The M4 iMac isn't only a better-specced machine than the M3; it's also cheaper. For $1,299 / £1,299 / AU$1,999, you get the 24-inch M4 iMac with an M4 chip (8-core CPU, 8-core GPU, and 16-core ...
Physically, it looks to have the same dimensions and proportions as the previous 24-inch iMac. However, that's not bad, since it gives you a slick display and stand, easy access to ports ...