The GeForce 9800 GX2 is the fastest graphics card at the moment and its performance easily and consistently surpasses that of the Radeon HD 3870 X2 (42% on average and between 33% to 57% depending on the resolution chosen). Today, NVIDIA has more experience than AMD when it comes to multi-GPU configurations, SLI being far more popular than CrossFire even if it targets a niche. That means certain games like Test Drive Unlimited, which aren't profiled by AMD's drivers, are profiled by NVIDIA. Most games run faster with the 9800 GX2 , although it's essentially just two 8800 GTS 512 MB devices with a slightly slower GPU clock, while the Radeon HD 3870 X2 is based on two Radeon HD 3870 devices with a slower memory clock. Yet, the two GPU designs are not in the same league.
Having said this, we do not recommend buying a GeForce 9800 GX2 for those who rarely change graphic cards and want to invest in a very high end card and keep it for a long time. There are times when a card like this should excel, like when games are played at high resolutions and with demanding settings, but the 9800 GX2 is barely better than a simple GeForce 8800 Ultra. The problem, as is the case with the 3870 X2, is the relatively meager 512 MB of memory, which is incompatible with very high resolutions and when antialiasing is activated. The numbers speak for themselves: the 9800 GX2 out performs the 8800 Ultra (with 768 MB) by 29% on average and up to 41% at a resolution of 2560x1600, while activating antialiasing at this resolution shortens the gap to 13%. Yet, for many games, it's the only mode that still isn't smooth and the 9800 GX2 doesn't deliver much.
At the same time, this is clearly the new very high end card from NVIDIA and it's sold as such. The Point Of View model was announced at €500 ($791) and even with the lower price announced by NVIDIA ($600), the price difference compared to the 3870 X2 that we can find for less than $400, barely matches the average performance gap. The price-performance ratio of the 9800 GX2 isn't the best and gets worse at very high resolutions. So, the card is in the very high-end price category, but it doesn't rank very high when it comes to price-per-performance.