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

[KongMysen]

I just won a no-loss Mage game, and I've been playing single stack most of the game. I Kited a little and found the Shield of Rekross on Verona + a Call Colloseus scroll, which I used for trolls.

My Lineup was:

trolls first...
Then dual stack of Black and Reds
The the biggest part of the game with EITHER a black or a red dragon
At Shettera and Reha + bosses I had a single stack of Black Knights.

game ended with Black Knights as my champion with 45% dmg
Black and Red dragon each did 20%

rest was divided amongst Trolls+ Demon Portal troops.

My point is, I guess the dragons were equally usefull, since they ended up doing the same dmg. I switched troops to get the no-loss battles and I suppose the dragons have been used 50/50