In the group I am playing with, my character is a level 20 Sorcerer with the Draconic Bloodline. Through this Bloodline, I obtain a special attack of Breath Weapon and automatic spell of Form of the Dragon III
The description for the bloodline special attack says
At 9th level, you gain a breath weapon. This breath weapon deals 1d6 points of damage of your energy type per sorcerer level. Those caught in the area of the breath receive a Reflex save for half damage. The DC of this save is equal to 10 + 1/2 your sorcerer level + your Charisma modifier. The shape of the breath weapon depends on your dragon type (as indicated on the above chart). At 9th level, you can use this ability once per day. At 17th level, you can use this ability twice per day. At 20th level, you can use this ability three times per day.
As I am level 20, the breath weapon will deal 20d6 three a day
However, if I were to transform into a dragon using Form of the Dragon III, it appears my breath weapon is no where near as powerful
You can use the breath weapon as often as you like, but you must wait 1d4 rounds between uses. All breath weapons deal 12d8 points of damage and allow a Reflex save for half damage. Line breath weapons increase to 100-foot lines and cones increase to 50-foot cones.
While in dragon form, the breath attack only deals 12d8 every 1d4 rounds.
Why are there differences in how much damage the breath weapons deal?