Fire Breath is powerful. Even more powerful if you get the power from the Throat of the World to give it extra damage. Frost Breath, I don't know really, I rarely use it, but it was barely effective to an Elder Dragon.
I remember using Frost Breathe and going WTF this isn't the right shout! What's going on?!? and then I realized the shout I wanted was Ice Form
I remember having level 1 fire breath and it wasn't that great, but doesn't it have lingering fire damage? Also, don't targets who are on fire take extra damage? So that could come in handy possibly. I'v enever had them level 3 though.
Fun Facts. 1. Destruction School perks boost ALL of your relevent elemental damage. This includes fire breath, frost breath and storm call. 2. Parthanax is more then happy to help you meditate on the meaning of Yol. EI, Fire. Combined with Destructions Fire Perks this yeilds a 75% boost to your firebreath damage and allows the 1 shotting of most midlevel enemies. (suprised myself by toasting a bandit marauder on adept diff)
Don't use shouts much due to beast blood but when I do I can usually clear away the weaker enemies but it sometimes seems like they don't do the damage I expect.
I guess I'll have to work on the destruction school then.