I guess it really depends on what specific situation you're in. WiFi is probably going to be fastest in the iPhone, but if you have an iPhone on AT&T's GSM and Treo on Sprints 3G network, the Treo has access to the fastest networkm though I can speak on specific browser bench marks. Basically, on a cellular network, the iPhone will be slow, but should be fast on WiFi, while the Treo has faster cellular options, but no WiFi, which trumps most cell data speeds.