xbitlabs made a fairly good cover-up on tessellation performance between ATi and Nvidia in current DX11 games :
http://www.xbitlabs.com/articles/video/display/hardware-tesselation.html
The difference between the two is between 5~10% at best , with nvidia being the one that has the upper hand .
however what really caught my eyes is that :
1-GTX480 has a
45% advantage over HD5870 in STALKER COP @ 1920x1080 , decreasing to
30% @ 2500x1600 .
2-GTX480 has a
68% advantage over HD5870 in AVP @1920x1080 , increasing to a whooping
81% @ 2500x1600 !
3-GTX480 has a
27% advantage over HD5870 in Dirt 2 @ 1920x1080 , decreasing to
13% @2500x1600 .
4-HD5870 has a
3% advantage over GTX480 in Metro2033 @ 1920x1080 without AA or AAA , with the situation being reversed @ 2500x1600 (GTX480 has a
3% lead) .
All games are maxed out with 4XAA and 16XAF except for Metro2033 , with 258.96 and 10.6 drivers .
I think there is something wrong with this piece , since when does GTX480 enjoy such a massive lead ? , I though it was merely 15% faster .