Why is Xfinity coverage better than Verizon?

We recently changed from Xfinity Mobile to Verizon, but we're noticing that there are places where we get no signal when we did before and are thinking of switching back. This makes no sense to me since Xfinity uses Verizon's towers. It's possible it has to do with Xfinity using their hotspots behind the scenes, but one place is in the middle of a park where there is no hotspot according to the map. So why would Xfinity's coverage be better? I don't get it. We're in MA.