I think the most important thing for an animal is the quality of its life.
This is the most important and really only reason I've stopped eating meat. I'm not so concerned about the death of animals, but rather the life they led up to that death. Unfortunately, most any animal that is on your plate today arrived there through a process of intense suffering.
Animals intended for slaughter are treated as a thing, a product, and only viewed as a living being to the extent required by regulatory agencies (which is very little, and the heads of those are often in bed with heads of meat companies, so its all kinda corrupt, but thats a different thread). Anything done to the animal is done only to enhance the quantity of the meat, change the flavor, and cut down on costs, and its all often at the expense of the animals welfare. The quality of the meat doesn't really interest mass producers.
Without delving into specifies and quotables, its worth knowing and repeating that nearly every animals on your plate suffers intensely. Read about it, research it, and even if it doesn't change your mind about eating meat, its very interesting and you can at least fully understand what it means to eat that hamburger.
And every time you eat or purchase one, its the equivalent of putting money in the meat companies' hand and promoting such horrible mistreatment on a MASSIVE scale. For this reason, I decided to stop eating meat. I had to stop giving away money to a cause I find so repulsive, a cause that is kept alive because I and others are willing to overlook that meat production companies get away with torture because it saves them money.
Read about it, read both sides of the argument. And not just websites, read books and research people have put time and work into, not just opinions.