My 2ct worth
A lighter aircraft will glide as good as a heavier aircraft. Glide angle is defined primarily by the wing design: L/D ratio is equal for both a heavy and a light aircraft and can be considered a wing property. Best L/D ratio or best glide is achieved at a certain speed, this speed coincides with Vmindrag and is proportional to the stall speed. A heavy aircraft will obviously require a higher speed to glide the same angle as a light one.
However, in normal jet airline ops we never encounter this situation. For a normal descent we fly fixed speed (lets keep it simple). Descending at this fixed speed the heavier aircraft will have a better glide angle than the lighter purely because it flies closer to its "Best L/D ratio speed". Obviously the lighter aircraft will fly more away from this speed a.k.a. Vmd, which means a significantly higher relative drag, and thus descent angle.