The problem with the scaling in the Retina Macbook Pro is that when you would really need more space, you don't have it. If you use Resolve or Final Cut Pro X, it is very annoying that the controls occupy a large portion of the screen when you would like to see the video in 1:1 pixels as large as possible. This of course makes it hard to see the controls, but I think it is worth it playing with this a little. At least my eyes are capable of seeing the very fine print and especially in FCPX where the controls are often bold fonts, it is even easier to see them even at the native resolution.
Read this article for switching the resolution http://www.everymac.com/systems/apple/macbook_pro/macbook-pro-retina-display-faq/macbook-pro-retina-display-hack-to-run-native-resolution.html
I have tested myself the Retina Displaymenu Link to RDM. It works great. It even allows switching my 2880x1800 panel to emulate 4K which is very nice. Well at least nice for seeing how much space I would have if I had a large 4K monitor. Everything obviously is too small to read. On the other hand, it also shows that the Macbook Pro is quite well capable of rendering the 4K scene without problems, including video on that resolution smoothly.
This way (by switching to native 2880x1800 resolution), you will have maximal space in Resolve too since Resolve insists of using only one monitor.