This is a tough one. Despite ATi's drivers having improved over time, nVidia is still superior in this regard. I've been using a HD 5870 with ATi's proprietary drivers and i've encountered multiple issues with 3D applications in WINE. Native Linux (Installed) games seem to perform very well, but if you intend to use WINE, stick with nVidia. I'm replacing my ATi 5870 for a nVidia GTX 480 specifically for Linux/WINE. Look, ATi is not HORRIBLE for Linux/WINE, but there are some refinements and small bugs/issues here and there that will cause unanticipated issues. If you refer to the application database for WINE, there are alot of games that are considered Platinum/Gold but do not work properly with ATi...but most titles in the App DB have been tested with nV cards. And there's too many forums/posts, even entries in the App DB, that indicate issues related to ATi users that nV users do not experience. You can go for ATi and, over time, start experiencing more stable/refined drivers, but if you intend on experiencing WINE now, go nV. r2rX :)
