Actually, yes :D. I didn't think about it. I completely forgot about their abilities. Considering... :D

But in general, comparing upgraded fairies and upgraded vampires, I think it's clear who it's more advantageous to play as and who has the upper hand :).

Although diplomacy is, of course, an excellent alternative :D. More money, and if you have native troops of the creature you want to recruit, that's a plus too, plus the "See Invisible" spell, and you're good to go!!!