Different compression, so the bitrates are not directly comparable. Due to that, the sample rate is much more relevant. GSM and g.711 (what the landline phone network use) are 8 KHz audio. AMR-WB (G.722.2) is 16 kHz.
I wouldn't call this "HD voice" (wideband at 16 kHz is far from "HD", you'd need ultra-wideband at 32 kHz to cover the entire frequency range of human speech), but it's definitely a huge improvement.--
Developer: Tomato/MLPPP, Linux/MLPPP, etc »fixppp.org