the x16 refers to the number of lanes it has, and im pretty sure its the same for AGP. but the real reason that PCIe is faster is because it is full duplex, something AGP could never accomplish.
PCIe X1-16 runs off separate lanes not connected to the PCI bus to improve bandwith, AGP ran off 1 lane using the PCI bus and just double, triple or Quad pumped the bus.
But if you were to look at benchmarks of an AGP GPU compared to a PCI-e the latter would perform better. I guess it's AGP's bus speed of 66.6mhz that holds it back.
AGP isnt dead yet, they are still making DX10 cards for the AGP interface, but PCI-E is newer, increased bandwidth, and is not going to be overtaking by AGP.
Thats like asking if PCI is going to overtake AGP...
i wish i had the link to the site that spoke about AGP having a comeback... i coulda swore i was on the Nvidia website... anyway... So the gist is that PCI-E is the product of tomorrow and AGP slots are going to be no longer supported by motherboards.
i think that motherboard manufacturers will stop putting AGP slots on their boards first, then eventualy the GFX card manafactures will disscontinue making AGP cards.
But like i said maybe in a few years time,Not yet.