The 580 can take more RAM, can take IDE HDDs and you can slip it's mobo into nicer cases like the 6400/6500 and connect a trinitron(if you like em) or any other display.That beats out anything the 575 can do. The 580 has an onboard connector for some video input thingy too. (yes, I know you can get that "presenter" kit for the LC575)
Case-swapped 580 all the way!