Seems like the Retina iMac can scale to 2560x1440 kind of like the Macbook Pro's. And it beats the 4 core nMP in some tests, including Cinebench.
I bought the first Retina Macbook Pro in 2012 and had some issues with image retention on the screen. Apple fixed it in the end but I am slightly wary of such a high-res new panel. I am considering it now though. I liked the idea of being able to chuck the new Mac Pro in my bag but maybe I could manage with this thing and a custom Peli case. Need to go check them all out in the store really.