When you supply a valid argument that doesn't contradict itself, then I'll cut said crap.
AGP uses the PCI bus. It shares its resources with other PCI cards at the chipset. If you have an audigy that spams the PCI channel with noise, it will affect your AGP card (though not as much as if it were a PCI card). AGP is said by experts as well as myself is far more unstable at 8x than 4x, and is the most stable when its GART functionality is disabled. Essentially, AGP is a dedicated PCI channel, which is overclocked by splitting the voltage across the cycles.
PCIe does not use the PCI bus. Its resources are entirely independant per channel, and PCI noise is non existant from one lane to the next. Because of the nature of power/signaling being separated from the datapath, a device does not become more stable by using more or less PCIe lanes. Essentially, PCIe is the successor to a strategy that is over 11 years old.