>>AMD/ATI and NVidia have been leapfrogging each other for about a decade now, stealing the
performance crown back from their rival every couple of months.<<
Not really: for the "pure performance crown", NVidia has been consistently the best since the
9700/9800 days where ATI was the best.
For the performance/price ratio (which is much more important IMHO), you're correct that both
are very competitive, which is great, especially now that AMD/ATI has opened its spec..