The GeForce 6800 series. Both the 6800 and 6800 GT owns the X800 Pro. The X800xt owns the 6800 Ultra by like 5-10 fps (which is hardly a noticeable difference if you are actually having fun). Plus the X800 Series uses Pixel Shaders 2.0 and 6800 uses 3.0, meaning that the 6800 might last longer for future games using 3.0.
In perfomance and also quality, they are both equal.
In technology, the 6800 "should" have the upper hand.
Resources are from Tom's Hardware.
Great news for all you nVidia fans with power supplies around 350w: http://www.gamespot.com/news/2004/05...s_6096837.html