The first major distinction between hot cocoa and hot chocolate is the temperature. Hot chocolate is heated to a point that the contents of the cheap styrofoam cup rival that of mercury's surface (around 1130 F) leaving your tongue a blistered and scared memory.If you are actually able to taste this igneous liquid you will find it quite bland. Many people have found that a few stale marshmallows improve the quality of the beverage. I find this unacceptable.
The last major difference (other than the overall lameness) is what resides on the outside. A sticky chocolate residue that clings to your hands like an overweight man clings to his hamburgers.