5. Less effort
There was a study about unshod running that looked at 35 barefoot runners and compared them to shod runners during two tests done over four minutes at 3.33 meters per second on a treadmill dynamometer.
The barefoot runners had far less contact and flight time, higher pushing and braking impulses, decreased passive peak force, and an increased preactivation of calf muscles. What does that mean in plain English? They worked less but still got as far as those in sneakers.