Bright pictures at night/in dark closets is important to some people, so is stable video recording. Not so important to the others, I'd argue most people don't take pictures in the dark. And with the daylight pictures as average as they are, the camera is no longer a selling point. This is where the importance of the form factor comes in. Two phones, almost identical specs, similar daylight rear camera capabilities... It comes down to brand loyalty or form factor.
I'm not trying to scream about the 920 being fat and heavy, I've never held either device. But if the 8x feels better in my hand or pocket, that's the phone I'd get. If the 920s camera was as good as nokia made me believe, my choice would be different. Looking at it from the reviews, the form factor of the 8x (as long and awkward looking as it may be) is more comfortable than the 920. If Nokia's killer feature isn't very "killer", why opt for the phone that I won't like carrying around?
Can't wait to handle these two in person...