Could be different phones and the bands they support, in part. My brother and I are both on T-Mobile, but he gets better data coverage in the U.S. (we both get

Could be different phones and the bands they support, in part. My brother and I are both on T-Mobile, but he gets better data coverage in the U.S. (we both get perfectly fine voice coverage). I have the "Global" version Moto G, which doesn't support either of: 1) any of the 4g/LTE bands, or 2) the 1700 MHz AWS band on which a lot of T-Mobile's 3g coverage is located. (The U.S.-version Moto G does support 1700, but then isn't usable for 3g in Europe, because it lacks 900/2100.) Whereas he has a Nexus 5, which supports LTE, giving him 4g coverage in some areas where my phone falls back to either EDGE, or no data at all.