I am very pleased with the ease of the PS/2. I have had no problems having to use a PS/2->USB emulator. If you plan on hardware multiboxing, PS/2 no doubt. If plain simple WoW interface is your game, then I would use the USB. I have tried both and the PS/2 is far simpler to setup than the USB, but the USB is easier to change on the fly, but lacks true mobility.