There was no difference between the Dragoons and the Dragoon Guards. The guards title was just a sweeting for the loss of better pay the former Heavies had to accept in 18th century. In theory the heavier weight of man and horse gives an advantage for the Heavies.
Light Dragoons and Hussars are tactical identical. The Lancer's arm was not realy an advantage. If the enemy was able to parry the stitch the Lancer was in a bad situation. Cossack are reputed to be able to fence with the lance, western European Lancers not.
The difference between the types of cavalry faded. In 1853 a new universal Sword was introduced for Heavy and Light cavalry alike. From my own example I can confirm the stories that the grip was not ideal, it tends to twist in the hand.
The Heavies had bigger horses, the Lights had more agile ones. But the Crimean war was bad for the horses, many ill or dying. The popular image of the helter skelter attack is far away from reality.

