i used to be a strategy analyst in the wireless industry and GSM is more adopted around the world (except the US - stupid reasons why GMS phones can't be global on one network) but at the time CDMA was a better wireless technology.

please note that I changed fields of expertise and no longer follow up on wireless - I'm not sure anymore as to that but know that the mobile broadband that Sprint has is on average 5x faster than Cingular or Verizon sometimes up to 20x faster

the most reliable network was the i-DEN technology (Nextel) but it was not capable of 3g upgrades but worked great as a cellular provider (my current phone is a nextel crackberry and I love it)