A console doesnt run any other processes or rendering other than the game, and perhaps the menu in the background, so a console can completely task off to a game to give its performance.
A PC on the other hand has the much higher power components, such as a dedicated graphics chip, a strong processor, fast access ram, etc etc. However since a computer has other tasks they MUST maintain, gaming is slightly bottlenecked.
In the sense of a XBone/PS4 vs Game PC, the PC would win hands down in terms of quality textures and physics, whereas a console is cheaper and preferrably has better games developed for it since companies like consoles over PCs.