I’m an athlete and a biomechanics student who studies this sort of thing. Technically, if you do the physics, yes, pavement is harder than dirt. Will your body actually notice that difference given the forces that you experience from an easy run in modern shoes? Not likely. For a few hours a day, day in and day out over decades, then yes you will. But if you run a few miles once or twice a week, no, you probably won’t see a huge difference. (And most trails frequented by runners are packed dirt that is not much softer than pavement. Getting onto shift and squishy loam tails isn’t feasible for everyone.)