Well I'm not 100% certain for AIW versions, but as far as the standard Radeon cards go, GET ATI!
non-ATI Radeons (and oem vs retail too) are clocked lower by default AND use cheaper slower RAM which also limits o/c a lot. Not only that but ATI are very thorough with quality of parts and build and result in great image quality that non-ATI cards are unlikely to have, although that diff will likely be small. If you can get a non-ATI card very cheaply then it may be worth it. As far as I am aware the TV chips used can change between the different PAL and NTSC standard used in US, Europe and the rest of the world.