Starlink is in a better position as their satellites are in a low earth orbit - 30 times closer than geostationary. It correlates to 1000 times (30dB) stronger signal on both sides.
Newer GEO direct-to-device satellites also have huge reflectors and often much higher transmit power levels that can compensate for the greater distance somewhat. Terrestar and Thuraya have had quite small phones available since the late 2000s already, and they're both (large) GEO.
Starlink is doing direct-to-cell. Talking to existing phones requires a large antenna. The bandwidth for each device is slow, not enough for mobile data, but better than Iridium. I think they recently showed off voice calls.