Question for the reviews team - Pure i2O vs Onkyo ND-S1

Hi. I was comparing the reviews for the Onkyo ND-S1 and the Pure i20. Both extract the digital signal from the ipod and so would it be fair to assume that there would be little difference in sound quality when comparing the sound quality of these docks through the same DAC? If so then why is the more expensive onkyo a five star product whereas the cheaper Pure product, despite also offering an on-board dac and video outputs, rated as four stars? Does the Onkyo somehow extract a better sounding digital feed compared to the Pure?