Wouldn't "PC law" stae even an identical port between the Xbox One and PS4 will run better on the PS4, even just by FPS merits?
If you run two PCs side by side, with the same game and EXACT same settings in-game (graphics level at ultra, etc), and both PCs have similar internals, but one with better memory/gfx, one game will simply run with a higher FPS. It might not look better as both PCs have the graphics levels set the same, but it will run better in regards to FPS.
Surely unless developers artificially locked the PS4 framerate, the end all and be all will simply be a higher framerate? They could say we are not bumping textures or MS will be annoyed, but they cannot stop a game running at a higher FPS unless it's artificially?