Which is more unethical: Raising animals compassionately, slaughtering them for meat as painlessly as possible after a healthy, happy life OR Letting people

Which is more unethical: Raising animals compassionately, slaughtering them for meat as painlessly as possible after a healthy, happy life OR Letting people who require meat in their diet to live (there are a number of reasons this may be the case) die slow, painful deaths as their bodies fail around them? It's real easy to say that "no one should ever kill an animal to live" when you ignore the disabilities and chronic conditions that make surviving on plants alone impossible, or prohibitively expensive.