The 140kv motor may be running at a lower efficiency at the same km/h speed, turning power in to heat instead of wheel torque. These motors can run as high as 85%, and lower than 60% if they are too heavily loaded at low RPMs. Pedro did some great work on efficiency charts but we don’t yet have a good way to put that into practical use like the ebike motor simulator based on the loads we actually see.
There are other factors that could also cause him to be slower too:
Larger tires
Heavier rider
Lower battery amp setting will limit total watts to the motor
Different throttle curves
Lower voltage
Most likely, a higher KV motor will improve performance though