The difference is more the missing AA then the resolution. also we should wait how the multiplatformers outside the launch window will look like. i dont think that the developers spend whole lot of time into their one and ps4 version. its impossible that ryse runs in 900p with AA smooth but something like CoD runs in 720p.
Its more than missing AA. Its that fuck of a sharpening filter, dithering, sub-pixel breaks and crushed blacks. Micrososft wouldnt have implemented all this bullshit post processing scaling if they werent 100% sure about the inferior hardware and the possibility that most games wouldnt run in native 1080p. They did this on purpose to achieve a "popping" picture, by destroying everything that makes a fine image. Ryse runs with inconsistent framerate under 30 fps, CoD runs in 60fps. You wont believe the amount of power it needs to achieve 1080p60fps in a modern FPS.