It's difficult to put one's finger on the difference between the two images..
One thing for certain though- frame 1669 is NOT the same frame between the two cards, which is odd. The blades of grass and falling leaves are in different locations, which makes it difficult to try and do exact comparisons here.
The thing that sticks out the most to me (besides the obvious color differences) are the tree leaves in the upper-right tree. On the GF-FX, the leaves are thin, sharp and smaller.. whereas they are fatter, more colorful on the ATI... but truly this could be a different perspective angle on the leaves if the frames are actually 3-4 apart from eachother, which looks like the case.
If anything, before anything objective can be arrived, FutureMark needs to comment on this, as well as clearer defined methods of reproducing these shots in an effort to hopefully reduce any possible human error if this is the case. It would seem that either:
1) The frame counter at the bottom right corner isn't accurate between different IHVs
or
2) If this is the result of some sort of "IQ" test built-in to the benchmark that captures an exact frame, there appears something faulty with it capturing the same, precise frame.
After all- differences in shaders and the like shouldnt cause a tree poly at location X,Y,Z in 3D space to be at a different location at the same rendering time!