If you are thinking of owning one of the three phones (Nokia Lumia 800, iPhone 4s, iPhone 4), do check out the Benchmark tests in the video. iPhone 4s is the winner of the three. However, Lumia 800 still excel in some of the tests.
Here are the tests done: Browsermark, Speed Reading, Sunspider, Acid3, and HTML5 tests. In real life, I guess these tests will not be useful to gauge the performance of the phone. However, it is nice to see high scores for your handset.