First of all:
1.AMD does use pci express. Most of their socket 939 motherboards have pci express. Only a couple socket 939 mobos have agp.
2.AMD is way better than intel. When you are talking gaming performance yes AMD is that much better.
If you go around this forum and ask people if they use AMD or Intel I bet you will see that 80% use AMD and like 20% use Intel. That is just in this forum though because most of the people here build gaming computers and gaming just goes with AMD.
New build in progress, but this is what I got for now:
-AMD x2 5200+
-Asus M3A78-EM AM2+
-Buffalo 2x1gb ddr2 800
-Hitachi 250gb Sata HDD
-Antec Minuet Case w/ 350w psu
-Windows 7 Home Premium 64 bit