The 5k display would be more versatile, however. Well, I guess that’s relative to …
I can understand why Apple is not in a hurry to sell this just as a display. This display could likely not be driven at all by all of their most popular Macs: all the MacBooks and the Mac mini. Maybe it would work with the Mac Pro, but that’s it. And that Mac Pro is probably not the best selling Mac, by a large margin. So they would basically sell this display that only works with a Mac Pro.
I can understand how that might seem like a wasted effort until at least a couple more widely selling Macs support the display. Maybe when the MacBook Pros can do it they will start selling just the display.
With the iMac the advantage is that Apple is delivering it with a computer that definitely can push those pixels, so you dodge all compatibility woes that will plague these high-res displays for a couple more years. It seems like the still had to get in there and do some weird custom stuff and maybe that’s just hard or impossible to do if you have to do it in a display that is hooked up to some random GPU from Apple’s past Macs.
Prior 27" iMacs have had the ability to run as external displays in Target Display Mode.
This was very nice when the view connection was DVI, but the current ThunderBolt connections limit it to other systems with ThunderBolt and the appropriate drivers. This limits it to pretty much using the display with other Macs.
My quick review of the Apple's tech spec for the new iMac doesn't say if it has this feature.
I had the worst time getting Target Display Mode to function sanely. I had thought that it was some kind of hidden systems feature or something, but at least at the time it required an Apple keyboard be attached and a specific key sequence be pressed during startup to make it happen.
On my mid 2011 iMac ⌘ + F2 enables target display mode once something is plugged in to the mini display port. Nothing needed at startup.
Not sure about having to be an Apple keyboard- probably works with any keyboard as long as you know which key is mapped to command. (Usually the "OS" key).
While you can use a DisplayPort display with a Thunderbolt iMacs, you cannot use target display mode on a Thunderbolt iMac with a DisplayPort 1.2 PC (or pre-thunderbolt mac).
I can understand why Apple is not in a hurry to sell this just as a display. This display could likely not be driven at all by all of their most popular Macs: all the MacBooks and the Mac mini. Maybe it would work with the Mac Pro, but that’s it. And that Mac Pro is probably not the best selling Mac, by a large margin. So they would basically sell this display that only works with a Mac Pro.
I can understand how that might seem like a wasted effort until at least a couple more widely selling Macs support the display. Maybe when the MacBook Pros can do it they will start selling just the display.
With the iMac the advantage is that Apple is delivering it with a computer that definitely can push those pixels, so you dodge all compatibility woes that will plague these high-res displays for a couple more years. It seems like the still had to get in there and do some weird custom stuff and maybe that’s just hard or impossible to do if you have to do it in a display that is hooked up to some random GPU from Apple’s past Macs.