I have done another test with the signal stats below and can see an improvement over serial mode:

“type”: “hdr”,
“rssi”: -125,
“ecio”: 5,
“io”: -106,
“type”: “lte”,
“rssi”: -49,
“rsrq”: -8,
“rsrp”: -79,
“snr”: 166

Also I have noticed when it looses signal the 3G / 4G LED stays lit.