jonny- you're missing my point, i'm saying the 8mp sensor is just a better sensor all around, and the additional resolution has a lot to do with this. it allows for much greater dynamic range in your images as well as much more detailed and sharp photos. the images are all around more crisp than the 10d sensor's. IMO, the second generation digic sensor and processing chips were a gigantic step forward in the digital slr world, just from my own experience.
You are correct in that it is a newer sensor that added dynamic range as well as detail versus the 10d. a lot of this depends on comparing apples to apples- the nikon sensors, while ccd's like the canon sensors are totally different beasts.
by the way, if you want to see something really impressive- look at how the 10d, 20d and 5d all handle shots in low light at 1600 ISO. That will give you some semblence of how far we have come in sensor technology.