One of images looks like it has more sharpening applied. Its why unsharp masks works when I develop images from RAW. The "native" image looks unusually soft. That explains it then. Its not the first or last time AMD or Nvidia have done this. For example PhysX on and PhysX off,when the latter had normal physics animations removed from some games,to emphasise the difference. Then you have had earlier games such as Red Faction which could do insane physics on old CPUs. Same with TressFX and Hairworks,software based hair animation techniques existed,but look at how flat the hair looks in games promoting such technology,without TressFX/Hairworks switched on.