Image quality is typically a pretty cut and dried affair but we see an interesting trick employed here that enables stable performance with a minor compromise to image quality. At its core, the PS4 version operates at 1080p while the Xbox One is 900p - but that's not the whole story. Ubisoft makes use of a "temporal filtering" feature that has a pretty interesting impact on the game.
Essentially, this feature renders the game with half the number of pixels on each axis with an ordered grid MSAA pattern before reconstructing the image to match the final output. This is then coupled with a post-process temporal anti-aliasing solution to minimize artefacts in motion. So, at 1080p, we're technically seeing 960x540 with 2x MSAA. Interestingly, it would appear that the image is processed before being upscaled on Xbox One resulting in blurrier HUD elements and menu text.
This trick has its drawbacks, but when combined with temporal AA, it helps produces a soft yet stable image in motion. If you slowly pan the camera around you can certainly spot edge artefacts but, during normal gameplay, this is much less apparent. The resulting image is actually more temporally stable than many other console titles. It's a fantastic trade-off here that really helps keep performance up without a significant impact on image quality.
