Hd 3870
ATI have had and still have a much richer colour palate and better Image Quality, ask any enthusiast that is open to both brands and they will confirm this.
nVidia tend to sacrifice IQ for performance, they will try to squeeze out every Hz they can at the cost of Quality,
Where as ATI have always been more partial to Image Quality.
Having owned many cards from both brands I can honestly say ATI win for IQ and Colour
This is only my opinion.
Another "eye candy" feature is Anti-Aliasing.
And the more AA you use the better ATI cards cope.
If you look at reviews of nVidia vs ATI cards you will notice that at 2x 4x or 8x AA nVidia cards will usually out perform ATIs
However in dual card config (SLI/Crossfire) the option of 16x AA becomes available and ATI suddenly out perform nVidia.
So Crossfire Scales better than SLI and nVidia cards can't cope with high levels of AA as well as ATI can.
This is not my opinion, this is proven.