Let’s be real. If you saw an orc, a zombie, or a giant minotaur with an axe in real life you would crap yourself and run away as fast as you could, screaming the whole way.
Horde clearly have an advantage at the character selection screen.
The intimidation factor. Some alliance are pretty skiddish for sure, but I’d say that comes more from a lack of confidence and a defeatist attitude. There is people that give up quickly, expecting to lose.