I'm at phone but I will try to explain the 3 OSs and VMs.
The Xbone will run a light and clean OS just to boot the hypervisor (the VM itself)... over it MS put two virtual machines:
1. VM running a light and clean OS windows customized for games...
2. VM running a Windows 8 customized for User Interface, Kinect, Skype, etc... everything not related to to the game will run in that OS.
The three OSs will have reserved 3GB of ram but they will not use all of them because there is a margin (1GB I guess) to install end run others apps without use resourses reserved do run games...
I'm pretty sure they reserved a number of CPUs cores to run these OSs and play the games too... the resources used by the OSs will never affect the gaming experience.
OP. There is no way to MS catch Sony in graphics terms this gen unless the game are fixed to run in the lowest power plataform (MS pay for these tricks) so the PS4 will run with unused resourses.
The biggest MS advantage was thd 8GB RAM but Sony because a lucky of the destiny can match that because the memory companies could release the 4Gbit GDDR5 in time to mass productiom of the PS4... if the memories companies have delayed the release 2-3 months the PS4 would only 4GB of RAM.









