What is better in a 1 unit army - 1 red or black dragon

[N3MES1S]

Red dragons always. They can be resurrected and can be improved by spells. Besides, red dragon are good against black dragon, but black dragons are not than good against red dragons (RD Are fire inmune). And, the red dragon special hability is more useful than the black dragon (almost for me). Maybe i always use red dragons cuz i have paladins and inquisit, but i really found em more useful than black dragons. I just changed royal griffins for assasins, and i almost never used the tank units lol, i only summon the avenging guards and let em to do the work. But god, i run out of royal griffins but assasins are amazing -.-. I love red dragons, but i dont use em too much, only to block enemy's way or for using the RD Hability.