Several differences between the Verizon and AT&T iPhone 4 have already been revealed, including changes in the antenna design and other components. What might surprise some people are actual differences in calling capabilities between the two devices. It's not clear whether or not these differences in functionality are due to Verizon's network technology or some other reason, however business users will especially be interested in these calling limitations.
Unlike the AT&T iPhone 4 pictured at left, the Verizon iPhone 4 doesn't allow users to swap between calls on hold when adding calls to a conference. In fact, both calls pictured here are simultaneously connected and must be hung up together on the Verizon iPhone. In contrast, the AT&T user can switch between calls or join them together to create a conference call.
Not only this, but the Verizon iPhone will only allow three callers (including yourself) to be connected on one call. AT&T does not exhibit this limitation, as it can connect up to six callers on one conference call. Although the Verizon network has a reputation for reliability, strong signals, and fewer dropped calls, there are other issues with Verizon's CDMA technology that may discourage AT&T users from switching.
AT&T subscribers are used to enjoying simultaneous data and voice calling on the GSM network. For example, checking your email while talking on speakerphone, or sending a contact via text message to a person you're speaking to has always been possible. Verizon users must choose between voice or data, meaning that if you're interested in browsing the web your phone call must end. Not only this, but Verizon's CDMA network has slower data speeds.These concerns don't factor in any travel overseas, but AT&T users will have the advantage there, too. GSM networks using SIM cards are prevalent in other countries, but the Verizon iPhone only works on CDMA, does not include a SIM card and is not a worldphone. These travel issues could be a moot point with the iPhone 5. Apple is planning to launch a hybrid iPhone that will work on either network.