which graphics card is better NVIDIA or ATI?

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every week a new graphics card comes out into the market and i am not knowing which card to go for. Every card seems to be good one with its own features and performance. Not only that I have heard directx 10 will be released along with vista and it's a talk that once directx 10 is released all games will be made compatible with directx 10 cards. I have seen some of the clips of games capable of running with directx 10 and they look very realistic too. I think directx compatible cards will be priced high. So is it a good idea to buy an moderately priced card that can play all games or should i wait for directx?