I'm not 100 percent sure but I think that verizon phones would be able to get a better recpetion on a verizon tower than a sprint.
Correct me if I'm wrong.
Posted from my CrackBerry at wapforums.crackberry.com
This is most likely the reason. 1x is what handles your voice amd SMS. EV is what handles data, to garrentee of data on the sprint device. it may happen byt your device may not be able to pick up the VZW data side.