[@Wick]
Lightning is more powerful then fire ;) 
Also side note lightning dragons are sought after by the scientists because of how much they can use from them and the scales are a bit different

Frost is also sought after

Water and fire are good but not as fantastic...earth is okay

There are other types of dragons but they aren't as well known as of yet

Edit: also I am not feeling well at all so may take me a bit to post
Especially with all the ideas I have going on in my brain