80 gb has software emu. 40 gb has no compat. 20 gb has the emotions engine, which is hardware emulation, but no wifi. 60 gb has the full ps3 package. Emotions engine, 4 usb ports, card reader, wifi, etc. I have a 20 gb ps3 with an upgraded 120 gb hdd, since I don't need wireless, and if I do, I have a wireless bridge I can use.