There has been a lot said about the speed of the iPhone 3G S, so we put it to the test versus the upstart Palm Pre's web browser. Thanks to at AT&T failing to activate our iPhone 3G S, we resorted to using WiFi for the test. This is only one test, using one web site. Results in the real world will vary based upon your wireless carrier. In fact, we're included a CNET Prizefight video where the results were quite different.
Both browsers are plenty fast. Unless you are carrying around two expensive smartphones and speed testing, chances are they will both meet your needs. We also ran a few tests between the iPhone 3G S and the iPhone 3G. As you'd imagine, the 'S' also won those tests handily.

