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

[DGDobrev]

"On a strong geyser user (level 3) it doesnt matter if u have red or black, they die anyways lol."

That assumption is completely incorrect. The Reds may die, but the Blacks are immune to magic, so the geyser won't hurt them at all. I have seen heroes casting geyser vs. single black dragon stack, but in the end, it's a wasted amount of mana because nothing changes on the battlefield.

Against Baal, both Red and Black Dragons are a really poor choice. Why would one want to use a fire-based attack creatures versus something that is 80% fire resistant? Or even against something that's 50% resistant (like most of the demons Baal summons)? If one does, it clearly shows a significant lack of tactical thinking on their part. Even peasants will be better than red/black dragons for this battle, as both of them will eventually die, but at least the peasants will inflict some damage due to their numbers and physical-based attack