Dilemma in Brazil

[frankinbahia]

I recently moved to rural Brazil where we have to rely on cell phone service exclusively. I have a CDMA phone from the major supplier (Vivo), but even with a Wilson amp the signal is rarely above one bar and frequently nothing.

Vivo has both CDMA and GSM (850mhz) service, and I'm thinking of trying a new phone. Vivo's local agent claims that their CDMA service is better out on the fringe where I am, but virtually all of the new phone they now stock are GSM.

Should I go with a GSM or try to source a new CDMA?

Thanks!