Droid 2 Global - Will switching from Global to CDMA-only improve battery life?
Since Verizon is CDMA-only in the USA, as long as your CDMA reception is strong there will be no reason for the phone to search for GSM.  If you find yourself in a very low/no-signal area, however, the phone may hop over to GSM to search, even though it cannot connect to any domestic GSM network.  There's no real downside to switching this setting to CDMA while in the USA, as long as you remember to make the switch back when you travel overseas.