Tests show the Nokia Lumia 920's refresh rate 5.4x faster than iPhone 5
The testing was done by MikroPC and used the Lagomin response time test to compare screen refresh rates for the Nokia Lumia 920, Apple iPhone 5, and Samsung Galaxy S III. The explanation of the test is a bit tough to convey, because the original page is in Finnish (and it should be noted that there's always a chance that the test could be skewed towards the home team, aka the Nokia, but the test seems reliable). Basically, there is an image put on the screen, then changed, and the "ghost bars" are measured to determine the refresh rate (fewer bars means faster refresh).
The tests also showed that the Lumia and the Galaxy S III didn't always draw everything correctly. The iPhone 5 had no dropped pixels, but the Lumia ranged between 0 and 5% dropped pixels, and the Galaxy S III between 10 and 30%. In the end the Lumia 920 had 0.59 “ghost bars”, while the Galaxy S III had 1.4,1 and the iPhone 5 came in well behind at 3.15. That makes the Lumia 920 display 2.4x faster than the Galaxy S III, and 5.4x faster than the iPhone 5.
Ultimately, the differences aren't all that big, but could be noticeable in the right circumstances.
thanks to Faisal for the tip!