"Aliens of ALNST are better than Humans of ZOMST"
Aliens of ALNST are aware that if their human-pet dies, they die forever. Everything the alien invested into the human will go to waste if the human dies. Therefore, the aliens in ALNST tried to keep their human-pets alive despite the constant abuse.
Humans of ZOMST are aware that if a Zombie gets fatally injured or if their body parts are removed, the zombie still won't die. Therefore, they test the limits of how further they can use those Zombies.
Aliens of ALNST are not "better". Humans of ZOMST have an advantage that Aliens do not. If the Aliens had the same advantage, they would definitely use it for their personal gain.