Assuming that the drag of a light vehicle is the same as a heavy vehicle, then the heavy vehicle would coast longer since the extra kinetic energy from the extra mass would take longer to dissipate. I think that the heavier vehicle would have higher friction from rolling resistance (more deformation of the tires and bearing resistance) but if it is not strictly proportional to the mass, then assuming lower, it should coast longer. I am assuming the difference in drag would be minimal particularly as they slow down.

Of course in space they'd all coast for the same amount of time.

Cheers,

rcomeau