For Drivers, nVidia was winning until the latest updates which are messing with profile settings. Unless OmegaDrivers come back, nVidia wins that.
Performance to Price ratio, must go with ATI. If it weren't for my CPU and Mechanical HDD, my 5870 would dominate.
OpenGL, nVidia of coarse, haveing a Revision 1 5870 won't do it right.
DX11 - ATI, except the 5870 I have which is Revision 1 has a tesselation problem, no point.
I still would prefer ATI, unless you want the best at the time it comes out and have the money, nvidia.