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

[Zechnophobe]

Player controlled red dragons are a lot strong vs ai controlled black dragons than vice versa. This is simply because red dragons per leadership do more damage, and have just as much fire resistance (80%). Also it is slightly easier to do extra damage with red dragon special ability than black dragons.

Honestly though, both are awesome, and you should use them each!