At the point of specification view, the only big different between these two is pk-600mj have a real "1.3 M Pixels or 1280×1024" sensor and the other one have "0.3 MP or 640x480". But, at real world! I just test 720 model and I like its video quality at Skype and I do not see 600 model at action!
My question is, Is there someone which test both model? and he/she can tell me which on have better video quality at video conferences???