"nv" is a travesty. If you want open source drivers with nVidia these days, you should use nouveau.
At the moment, the ATi open source landscape seems much better. The OSS drivers are stable and working, up to OpenGL 2, and 2D performance is great. Due to lack of help from nVidia, nouveau is not quite as good at this moment.
Sabj. Now, I am using nvidia with 'nv' driver. I don't play games. I'll buy new video card soon, and I plan to use open source driver too.
What video will be the better choice?
ps My kernel config has disabled 'CONFIG_MODULES' option.
Is there any reason you are using the open source driver? The binary driver is much better and you are less likely to have issues with it. I am not sure if your purchase decision will have any effect on whether or not companies make open source drivers, so I have trouble seeing your rationale for using the nv driver.
With that said, open source drivers for ATI's graphics cards are better than open source drivers available for Nvidia cards. Like pingufunkybeat said, this is because Nvidia has not given any support to the development of open source drivers for its products. The closest they have come to this is making the wrapper for the binary driver visible source, so that its customers can patch it themselves should new kernel versions break compatibility with older kernel interfaces.