In my practical experience, I have found the converse to be true.
My Nokia N73 under Pune's iDEA cellular's GPRS plan, via a CA-53 USB cord, connects at 460.8 kbps. It uses GSM EDGE (Enhanced Datarate GSM Evolution).
My Tata-Indicom Huawei CDMA aircard never connects above 230.4 kbps.
click on image
Ram