Update: for those who were concerned about the battery affecting the Nexus One's performance, we did use Android System Info to verify that the CPU was still clocked at 1GHz. We were also able to reproduce the same results with a full battery. Either way, it's still a win for Android.
Our test candidates were a 16GB iPhone 4 (with a shameless color mod) and a Nexus One rocking the official OTA 2.2 update and Flash 10.1. Naturally, we cleared out the cache files on both devices prior to each trial. Out of the five desktop-version websites that we tested for load time, three of them -- BBC News, gdgt and The Onion -- repeatedly produced a tie between the two phones, whereas the iPhone 4 consistently loaded Engadget about two to three seconds faster, and the Nexus One about one to two seconds faster with New York Times. Here's our video of one of the trials:
Apple iOS 4
Apple iPhone 4
HTC Google Nexus One