The number of transistors you need decreases with each additional pipeline you add.
My guess its that the change occured because the 6 pipeline design was only as good as the R300. They want something better. And now both cards have 8 pipelines. My only worry here is that nVidia designed the memory controller around a 6 pipeline design and will now have to find a way to increase the bandwidth in order to feed the extra pipes. 256bit bus anyone?
Folding for Beyond3D
"A lie gets halfway around the world before the truth has a chance to get its pants on."
Sir Winston Churchill
"Halflife2 got halfway around the world before Gabe had a chance to get his pants on."