This question has been asked repeatedly around these parts. I suggest you search the forums a little and you'll find your answer.
yep yep asked lots o times but ill still answer..i was a ATI fan i still like ATI that all in wonder card the 9800 and the x800 r the sh!t i love them but with SLI my heart has moved to SLI and i plan to build an SLI system soon
But ATI has crossfire, so what extra benefit is SLI? GeForce definitely has the top ranking card (the best scores and the best game performance) but ATI cards are more founded. They experience less errors and are generally more reliable in my opinion. I still am using a 9600XT All-In-Wonder. It is so old but still runs every game. Maybe not at the highest settings, but its still not bad for an AGP.
Crossfire does not run as well as SLI, it is buggy. Also, the X1900XTX beats the 7950 in quite a few tests. But, considerthat you probably won't get a $400+card, you want to know about the midrange. Well, the X850 series probably wins the midrange value right now.
It depends on what you want. -nVidia strengths: -Quality Linux drivers -Quad-SLI -SLI maturity -Strong OpenGL support ATi strengths -Impressive hardware -Fastest single GPU on the market -Strong D3D support ATi's weakness is Crossfire's maturity. It was released much later than SLI and the driver development shows. It's much better than it used to be, but SLI still is a little more polished. In general, ATi's achilles heel has been drivers, but overall, they're much more on par with nVidia these days. ATi has consistantly had hardware that is simply better than nVidia's, but they've short changed it with bad drivers. Lastly, ATi's Linux drivers are...well...crap. nVidia tends to rely on more brute strength, and their GPU's are as optimized on the silicon as ATi has.
