Just went hands on with the L920 and 8x for 1 hour...
Live in SE Asia and MS is doing a tour with a few W8/WP8 products this week. Got to see the L920, 8X, Acer S7 (amazing!) and a few other midrange W8 notebooks. Here are my initial thoughts:
Both were equally quick and responsive. Really performance is exactly the same (as you would expect).
What I liked about the 8X:
Thinness and pocketablity
Fit and finish feel really good
I personally liked the 8X "blue" the best out of all the colors I saw for the phones
Power Button on top was a pain to access
16:9 felt a bit odd in my hand but probably would be good after a few days use
What I liked about the Lumia 920:
Screen is best in class. Honestly this is totally understated in the reviews.
Fit and finish were a step up from the L900. Definitely felt thinner than the L900 but was a bit wider.
Camera is a setup from the G3 which I had nearby. I could only test with a few shots in the store but it dealt slightly better with the difficult lighting in the store.
Button arrangement is excellent making one handed use very easy even with a 4.5" screen
Heavy in pocket
The yellow and red are amazing, but too bright for daily business purposes (IMO)
My overall thoughts are that FINALLY there are some great choices. If you want something small and pocketable - 8X is for you. If you want the best phone it is the Lumia 920. Neither phone completely destroys the other (as you might have read here number of times). If you are switching from the iPhone 4 or L800 the new L920 will feel really big and perhaps the 8X will be the better option... Putting the 3.7-4" screen phones next to the screen of the L920 and you will realize why some people will choose a bigger phone. In other words - different strokes for different folks. All told, I was very excited by both and will be purchasing the L920 as soon as it is available (4-6 weeks time).