At a bare minimum you’re looking at a $500 price difference between the 21.5 and 27-inch iMacs, which is pretty substantial to begin with. There are two reasons why you’d opt for the 21.5-inch iMac vs. While I’d prefer something with an insanely higher resolution, it’s still too early for a 21.5-inch 4K panel (or a 27-inch 5K panel), which Apple would likely move to in order to bring Retina displays to its desktops.

Given how much time I spend on notebook displays these days, now was as good a time as any to go back to a 1080p desktop display. With the new 27-inch iMac looking a lot like last year’s model with evolutionary upgrades on the internals, I was obviously drawn to the new 21.5-inch system because of its use of Intel’s Iris Pro 5200 graphics so I ended up with the first < 3MP desktop display I’d used since the release of the first 30-inch 2560 x 1600 panels years ago. At the time I was using a 27-inch Thunderbolt Display and couldn’t see myself using anything smaller, or lower resolution. When it was first announced, I shrugged off the 21.5-inch iMac model.

Late 2013 imac retina