Comment wise, one of the most popular posts here is about Cell Phone technology.  The comments have drifted in to cell phone protocols.

There are two main protocols, CDMA and GSM. CDMA is a legacy protocol only used here in the US. The rest of the world uses GSM.  This is an issue for hardware manufacturers, since the phone has to be built to support one or the other.

At least two of the major US carriers, Sprint and Verizon, still use CDMA.  So there still is a fairly large market for phones designed to use CDMA.

AT&T bit the bullet years back and coverted their network to GSM.  This probably gives them a slight advantage in pricing when buying phone in bulk from manufactures.  It also allows them to compete in the International market, since their phones will operate outside the CONUS.

Another advantage to GSM is the SIM card.  The part of the phone that identifies it to the network is designed to be an enduser replaceable device.  This makes the actual phone independent of the network (something that gives Verizon execs and Steve Jobs nightmares).

My iPhone, and my previous phone are both GSM devices, so I was able to take then SIM from my iPhone (Apple bricked it for about 12 hours) and put in my RAZR phone.  You can’t do that with a CDMA device.

Just from a technical, networking engineer viewpoint, my vote goes for GSM.