iLounge has completed its initial 3G cellular data speed comparisons of the iPhone 4S across all of the available U.S. carriers. As seen in the graphic below, the data speeds seen on AT&T’s HSPA network—between 2.41Mbps and 2.99Mbps down, 0.68-0.81Mbps up at our Buffalo, NY test location—far outpace those seen on either Verizon’s or Sprint’s EV-DO networks in the same area. Between the two CDMA carriers, Verizon fared better save for one outlier, with download speeds ranging from 0.55-0.69Mbps down and 0.04-0.26Mbps up, compared to 0.33-0.58Mbps down and 0.11-0.22Mbps up for Sprint. As was the case when the CDMA iPhone 4 was released, it appears that AT&T has a significant edge in 3G cellular data speeds relative to its rivals. LTE networks and LTE-supporting iPhones will most likely be necessary to let Verizon and Sprint bridge the current performance gap.