Today I received the LG 5K monitor co-developped by Apple and LG. Apple have stopped producing and selling monitors. This means the only 5K option from is the iMac 5K. So when the long overdue ending of the Thunderbolt display was decided by Apple they decided to work with LG and over a special monitor to work with the new MacBook Pro 2016. This monitor only has tb3/usb.c ports and it can charge the MBP 2016 15" with the supplied TB3 cable. The monitor is 27" and the DPI is 218 where the MBP 15" is 220 DPI. The colour space is P3 like the MBP 2016. The maximum brightness is the same on both screens. I calibrated the LG screen the same way as the MBP screen with my Spyder 4 unit and for the same brightness. The result is that they look very closely the same. It's not that different from my Dell 32" 4K screen after calibration, but the resolution difference is quite big. The DPI is 218 on the 5K screen and on the Dell it is 138. So a huge difference and it shows. After having the 32" I find that 27" is a more ideal size for me. I find the higher resolution pleasant to look at. Photos look really great on this display.
Set the monitor scaling in the monitor preferences to 2560x1440 and images will be displayed pixel perfect at 5K resolution zoomed into 100% or 1:1 for checking sharpness. 4K screens need full HD scaling to be pixel perfect at 100% or 1:1. This means large fonts on a 27" or larger screen, so in my opinion this is not ideal. 5K fits perfectly.
Design is not at all like the iMac 5K or the old Thunderbolt display. But the screen itself looks gorgeous. It has built-in speakers which are not that great, but usable for speech, but not really for music.
The price is discounted until March 31st at $974.
So if you are looking for a single machine solution and a MacBook Pro for photography then the 15" MacBook 2016 and the LG 5K screen is a very good solution.
The LG 5K is officially only supported with the MacBook Pro 2016 https://support.apple.com/en-us/HT207448
. I did connect the monitor to my previous MBP mid 2015 and it did run 5K from what I saw using a TB3 to TB2 adapter. But there maybe other compatibility issues, so the safe bet appears to be to use a MBP 2016.