Where are you?
I like CDMA because it allows me to get reception inside my workplaces. The types of labs I work in are typically built like bunkers, and GSM signals don't seem to penetrate as well.
I will admit that my experience with TMobile was that they were the least expensive and I had the fewest dropped calls.
Sprint was okay, their customer service was useless, and I'd get dropped calls but could call to get up to $5 of credit each month for those dropped calls.
Verizon is the most expensive and I seem to get the most dropped calls with them. Most of the people I call have in-calling, though, and it's worthwhile to me and them that we all stay with Verizon. If I left Verizon, I'd go back to Sprint.