Oh? Does that mean 2G in a lot of ways is better for calling? Since it has better coverage.
If that's the only criteria, then yes.
Otherwise, 2G and 3G use the same codecs for voice calls. The difference is, you can pack more calls together overall in a 3G network than you can on 2G, because it uses the available bandwidth more efficiently.
The one variable that can make things different is how the carrier has set up their network. They can set different levels of compression on different parts of the network. So, if a carrier decided to use higher compression/lower bitrates on the 2G network, and lower compression/higher bitrates on 3G, then 3G would calls end up sounding better. AT&T (then called Cingular) did this for a while pre-iPhone, when they first deployed 3G. Probably to spread the myth that 3G voice calls were inherently better-sounding, and to get people to buy more 3G phones where it was available.
Or, a carrier could just as easily do the reverse (even though that would make little sense) and 2G calls could sound better than 3G calls.
In most cases though (like AT&T today), carriers are well aware of the fact that more data is going through their network than voice calls are. So, voice calls are now compressed to the maximum levels they can get away with on both 2G and 3G systems.
