This is from another forum, but it wont let me post links because i'm new
It is a good explanation. it's over on incredibleforum dot com thanks to luv2increase
EVRC-B is an advanced, new and better audio codec than regular EVRC. Verizon started rolling out EVRC-B in 2007. The people who have bad experiences with doing this settings change are either:
1) Not in an area of the country where EVRC-B has been implemented yet
2) A little too far or just on the outer edge of the EVRC-B range
For those within the viscinity of EVRC-B capable towers, we are "LUCKY"
Why are we lucky? Well, it is a "fact" that EVRC-B will allow better call quality. That is one of the reasons it was designed and implemented!
It was posted earlier, but here it is again just in case some of you didn't see it from page #2:
Enhanced Variable Rate Codec B - Wikipedia, the free encyclopedia
I suggest everyone read that and to make the settings change. If you have worse quality or no reception, then just change it back. Apparently, Verizon hasn't made it to your area yet, unfortunately.