The strongest of the Dragons is actually
Rith, The Awakener. It saw a fair bit of play in
Fires and
No Fires decks back in the day!
That could be due to the fact of other ramp cards in standard (and that blue black control does not need a big beater). In draft I do not know which is stronger, they are both by far the strongest dragons.
In draft:
Trevas ability is weak, you get 4 ish life?
Darigaaz sucks, the opponent has only a few cards in hand.
Crosis is weak, but works with all the return cards in the block. You could discard the returned cards.
Rith is strong, it snowballs.
Dromar is stronger. It prevents the crackback, even against rith (If playing against rith, you could let rith through, and on your turn attack and return rith and all tokens, the opposite does not hold since you can return rith).