Computerworld is reporting that AT&T iPhone users are experiencing the fastest data speeds. Take a look at the chart above.

AT&T was twice as fast as Verizon in Web browsing with the iPhone 4S, recording average page load times of 1.29 seconds, compared with Verizon’s 2.60 seconds. Sprint’s version of the phone took an average of 6.44 seconds for Web browsing page loads, according to Amit Malhotra, vice president of marketing at Metrico, in an interview.

The study concluded that if one were looking to purchase an iPhone, the order of preferred carriers would be AT&T, Verizon then Sprint.

The iPhone 4S actually has the capability of using AT&T’s “4G” 14Mbps network while both Sprint and Verizon are stuck using their old, 3.6Mbps 3G network so seeing AT&T dominate speed tests is no surprise.

Verizon has focused all its effort on 4G LTE technology rather than investing in its 3G network. This will give it a large advantage and lead come next year when the iPhone 5 is equipped with LTE capability.