In terms of raw image quality, the 808 is better than the 1020.
I've done my own tests, I've looked at 100s of images from both phones, and on a per pixel level the 808 has more potential. Also the xenon flash/white balance on the 808 is better as well. You could say that I am just trolling or whatever, but honestly I don't have time for that kind of bs, and in general the most important thing in a smartphone for me is the camera.. so I don't care who makes it, if someone comes up with a camera better than the 808's tomorrow, I will buy it right away.
What the 1020 has over the 808 is image stabilisation and much improved low light performance, in a package running a modern and lets face it, better OS in a much better looking body.
I am sure that Nokia will fixe some of the issues with the 1020, but despite that... it will be hard to compensate for a smaller sensor and a weaker xenon flash. So.. I will pass on that one... maybe Microsoft can pick up where Nokia left off with the 808 and bring us a water (including salt water please) resistant smartphone with 1" sensor, decent optics, and a fat xenon flash
AS far as the OS, transitioning from Symbian to WP can be rough, especially if you are comfortable with Symbian. Its a very powerful OS and it still holds its own.. in fact, I just played around with iOS 7 running iphone 5 and I can tell you that Apple took a very close look at Symbian Belle FP2. Ultimately it depends on your expectations and needs when it comes to the software..
WP has a superior browser, more games, and arguably a better overall UX.. but that one is kind of a personal choice to be honest. Symbian, combined with the 808's hardware is very hard to beat.. as surprising as that sounds..