Did a little comparative test on my 3-year-old D70 and a D80 at a night shoot.
The newer D80 did much better at light sensitivity and dynamic range.
The CCD also replicated colours differently from the D70.
The D80 shot.
The D70 shot.
Both shots were taken at 77 seconds, F22.
ISO for the D80 was set at 100 while D70 at 200, the lowest for each camera.
Shadows/dark spots (see areas around windows without light on the blocks and trees) were generally brighter compared to the shot by the D70.
Technically, the D80 is one stop faster than the D70 in this shoot.
Note: This experiment was done in a rather uncontrolled environment. That said, the findings are solely “measured” with the naked eye and thus should not be a conclusive result.