First card is an 8800GTS where as the second is an 8600GTS, yes the second card has higher clock rates but half of the bus size(128) where as the 8800 has 320. the 8800GTS is is faster. some one correct me if im wrong but bus size is like a measure of how much data is able to be transfered between the GPU and main board. So the bigger the bus size is the more can be transfered. Its like a high way, the 8800GTS is a 8 lane highway, where as the 8600 is a 4 lane highway. Obviously the 8800 willll get more people to their places faster.
Exactly as they said, but as per 8600gts/8800gts example: the 86gts only has 32 shaders where as the 88gts have 112 or 128, therefor making up for the slightly lower mhz and offering waaaay more performance.