To your question:
These phones have a lot of similarities. The 8X has better Rez and PPI, they both have 8 mp cameras in the back, the 8X has the wide angle 2mp camera in front(which I personally love), the 810 has storage of up to 64G whereas the 8X is locked with 16G and whatever you feel comfortable putting on the cloud. The 8X also has the beats audio amp and speakers for sound.
I think, and many people will agree, that the 8X is the sexiest of all the new windows phones. I think the 810 is really nice. I think out of the 822, 820 & 810, the 810 looks the best. It's a very sleek, clean looking device. One which, as I look at it more, kinda think I might like to own.
Hope that helps