From the look of the rear panel, neither of the two Onkyo's you mentioned has analog pre-outs.
The 607 has more HDMI inputs and has dual sub pre-out. Overall, the feature set is more or less equivalent with some being margainally better than the 605, like the Audessy Dynamic Volume and Ipod connectivity.
That said, the 607 weighs slightly less than the 605. It might be argued that the 605 has a more robust amp section, but if this will make a perseptable difference in an actual listening situation is unlikely.
So, there you have it.