More importantly the 808 has a much larger sensor.
Exactly.
Now.. the 808 is kind of an odd case really, from a technical point of view anyway. Here is a bit of background info, and I will get back to it:
There is something the industry has been doing for years, and I blame the marketing departments for it. They've been concentrated on increasing the number of pixels, because they gradually made the consumer base believe that the more pixels you have, the better the quality, which is not necessarily the case. So they've been increasing the number of pixels, but that rate doesn't correspond to increasing the size of the sensors, so now we are down to 1.1 micron pixels.. which is why they have to use BSI sensors, but that is another topic.
The size of the sensor is much more important, which is directly related to the size of the pixels. The bigger the pixels, the more photons they collect, the more photons.. less noise, better quality.. That is why the DSLRs shoot at 4.0+ micron/pixel and go up to 6.x
Instead of the megapixel count, they should have marketed the pixel size .. "blalal 2.5 micron pixels, auto focus, blalal"
Here is a great little website on the subject:
http://6mpixel.org/en/
Here is a nice graph of the pixel sizes in various cameras
as you can see, big pixels in the higher end stuff... now, I am NOT saying that big pixels is all there is to it, far from that.. but its a very important part of it.
Back to the 808 .. both the 920 and the 808 shoot at 1.4 micron pixels, so therefore the size of the 808's sensor shouldn't matter that much, and it doesn't.. if you take a look at a full resolution 38Mpix image from the 808 and you compare it to another 1.4 micron pixel image, you will find that the difference is very little.
What Nokia have done is quite brilliant actually, they took that huge number of pixels, which was needed for zooming, and decided that they can combine 6-7 pixels into one in real time, so that the produced pixel can act like a bigger one, even tho the sensor itself is cut into 1.4 micron pixels. In the process their algorithm cleans up the noise, and whatever other garbage the pixels collected, and you end up with a.. more "pure" pixels in a sense, hence the name "PureView". That is only possible when you shoot at 5/8Mpix mode..
Here is how it looks like:
This is why the 808 outperforms all 1.4 micron pixel cameras out there, and some dedicated mid range P&S as well.. its .. pure magic.