Of course EVRC-B will sound better. It is a new vocoder that is more efficient and sounds better. The problem you have is that not all cell towers support EVRC-B, especially the older towers. If you are on an EVRC-B call and move to an area where there is EVRC only, then the call will drop if you have you phone configured for EVRC-B only. The best bet is to leave this function alone and allow Verizon to deal with it. The overall gain in call quality is not worth the risk of dropped calls.