Networks like Verizon’s that use the CDMA technology cannot transmit voice and data simultaneously, so Verizon iPhone users will not be able to look up directions or check e-mail while on a call, for example, as they can with AT&T.
The Verizon phone will also not work in nearly as many countries as AT&T’s version, which uses GSM technology. But in other respects, they will function much the same.
ATT > Verizon