What does it mean to handle HiDPI content?
The screen of the M3800 is truly enticing. In my opinion, the 1440*900 display area of the rMBP is a bit too low (I have a 1680*1050 screen on my mid-2010 MBP) and the 1600*900 effective area of the M3800 just hits the sweet spot. Plus, it's touch sensitive. For many professionals here, the Quadro k1100m might be the clincher. However, the one thing that the rMBP has over the M3800 is the OS's integration with the hardware. Windows isn't the best operating system for a personal system. Furthermore, as the article itself states, many of the prized features of the M3800 (screen (resolution), touchscreen, trackpad, etc.) are really pulled back due to bad drivers.
As a whole, despite the relatively high price and (comparatively) not-so-great specifications, the rMBP wins with OS X and Apple's monopoly over Mac hardware, which provides the best integration possible.
I would almost definitely go with the rMBP.
I hope I'm not hijackin the thread, but I was wondering what's your battery life like?
I keep it at 1680 x 1050 and my battery life kind of sucks