It's the same antenna in both the Verizon and AT&T models (it's actually just one model). So the Verizon model is capable of edge, 3g, 4g, whatever that AT&T has, and the AT&T model is capable of CDMA (not if it's locked, and even if it isn't it Verizon may not let it on the CDMA network because they're jerks like that).
This is why I'm not sure why everyone is saying there is no unlocked phone available - the Verizon iPhone 5s IS fully unlocked.