Waas (wide area augmentation system) is a form of differential correction. It is satellite based and decoded by the gps reciever as opposed to the radio based diff corrections. Waas is generally accurate to around 2-3 meters where as the radio based signals may be a little more accurate depending... Id say go waas as you only need the waas ready gps reciever and the corrections are recieved by your gps antenna, as opposed to the radio antenna and decoder, plus gps reciever of the radio based system. Hope that helps... Chris