GSM vs 3G | Phone/Device Issues and Features | Consumer forum

For voice, I would concern myself more with the phone than if it is 2G/3G. For the most part, Nokia and Motorola make good sounding low end phones. I would stay away from any Korean phone, because voice tends not to the strong point of those phones. Expensive smart phones tend not to be the best voice phones. The iPhone is close to as bad as you can get, but it is still not a horrid voice phone.

Generally, 3G phones are supposed to have better voice quality, but are harder on the battery, but I have a good sounding 2G phone, and my 3G phone has good enough battery life. As iamdrumming said, it depends on the phone more than anything.