Your Race in Dreamlords is more than just cosmetic, each race has their own strengths and weaknesses and one is not inherently stronger than another.
There are 3 races:
Covenant: Some of the strongest defense and highest morale points in the game. Has strong ability to heal. Generally lower attack power.
Nihilim: Strong ranged attacks. Suffers lower morale in general but DPS usually higher.
Thul: Speed and agility. High health points and attack power.