Again, like HazleNut, assuming level flight
Looking at the graph above...
Let's put a value of the minimum drag speed depicted on the diagram (courtesy of wikipedia) as 230kts for the heavier aircraft and 210kts for the lighter one.
So a speed of say 300kts will be a long way to the right of the minimum drag speed. As speed decreases AoA will increase. As AoA is increasing, initially its getting more to its optimum AoA. Form drag will be decreasing at a faster rate than induced drag is increasing ie. total drag is decreasing. As stated by Microburst the heavier aircraft, initially, is continuously flying closer to its optimum AoA than the lighter aircraft. Therefore it will be experiencing less total drag than the other aircraft and thus decelerating at a slower rate.
However once airspeed goes below Vmd for the heavier aircraft induced drag starts increasing at a faster rate than form drag is decreasing and so there is a rise in total drag. In the meantime however the lighter aircraft is now getting closer to its Vmd and so this aircraft will now start decelerating at a slower rate. Once both aircraft are below Vmd, I could well be wrong here though, I guess induced drag becomes the major player, the heavier the weight the more lift required. More lift = more induced drag = an increased rate of deceleration for the heavier aircraft.