I can also attest it makes a difference WHERE you are on the hill. My son sometimes had to go outside just to get a signal and other areas he was getting four bars INSIDE his room. He had TMobile and ATT. I'd go with ATT.
@Sneak you get your phone back after BCT. @hk.nguyen my daughter has Verizon and it works great. I think it depends on which building you are in though.