For Starlink the User Terminal (antenna a.k.a. "Dishy") is a phased array. It tracks the satellite as it passes from west to east. Each satellite is in view for around 15 seconds - the phased array instantly flips from east to west and acquires the new in-view satellite in microseconds. There's no degradation in almost all 'flips' especially if the U.T. has an unobstructed view of the sky.