OK guys, I'm gonna enter into this discussion. I know that people get very protective of their little GCN, and rightly so because its a cracking little piece of hardware.
I'm sorry to break it to you, but XBox is more powerful. The guy also makes several mistakes in his article.
Firstly, XBox does not implement bump-mapping via its pixel-shaders. Like GCN, XBox can perform bump-mapping in hardware, though they probably could be used to perform bump-mapping. It can also do environment mapping, and does a superior form to GCN - cubic environment maps. Ever wondered why the reflections in Mario Sunshine are so bad? It's because GCN isnt very good at environment mapping. XBox does indeed also have better textures - one look at Halo's righer resolution textures will tell you as much. This is because XBox has more RAM to store larger textures than GCN. HOWEVER, XBox does not have quite as good texture compression as GCN. This does cut both ways though. Increased texture compression means that the textures turn out worse. There is no way to compress a 1Mb texture down to 500Kb and keep a similar quality, sorry.
Also, the 'article' fails to mention that the integer performance of the XCPU makes the Gekko look like a lemon in comparison; 1980MIPS vs. 1125MIPS. Doesn't mean a lot, you say? Well MIPS are what make good physics. Which is always nice to have - good GFLOPS will get you nowhere.
Other advantages of the XBox over the GCN include higher GPU clockspeed (233MHz over 162MHz) and, of course, much much greater GFLOPS. The way that the nVidia chip does this is by not actually performing the calculations, but by looking them up in a table system. So powerful is the XGPU that it actually wastes cycles making mistakes, and STILL pumps out similar looking visuals.
Then, there's the actual, visual proof, and theres plenty of it around: Soul Calibur 2, Wreckless and Splinter Cell all look much better on XBox, often running at higher resolutions than the GCN counterpart and with more detailed models and textures. So much for 'no proof'. Halo 2 is much more visually impressive than Metroid Prime and is more technically advanced. XBox is also the only console to get cutting-edge PC games such as Half-Life 2, Deus Ex 2 and DOOM 3. John Carmack said that the only reason hes doing it for XBox and not the other consoles is simply that the XBox is the only console with enough power to play the game satisfactory.
The article also failed to mention sound performance, which is also an affecting factor. The XBox has a far superior sound card to the GCN.
Also, I HIGHLY doubt that Rebel Assault will have 10Million more polygons per second. That kind of increase isnt possible. RL slowed down quite a lot of the time, and thats with a claimed 15Million polygons per second (there's no proof of that though). 10Mil more will make it run like its bogged down in treacle.