To submit an animal for slaughter, the kind of treatment and feed it receives during its life is important. No abuse, mistreatment or infliction of any pain should take place towards it while it's alive. It should not remain trapped in an area where it cannot move or walk freely around or get fresh air. It should receive clean water, food, and never fed another animal or products that contain the by-products of other animals.
The halal method of preparing an animal for food allows maximum drainage of blood from the animal's body. Blood in meat makes the meat more susceptible to putrefaction and also negatively impacts the taste.
Stunning the animal before slaughtering causes it to secrete lactic acid which hastens the onset of decay. Lactic acid makes the meat less resistant to bacteria, which is why Halal meat has a very low rate of incidences of food poisoning. Non-halal meat in supermarkets and fast-food chains often has e-coli, bacteria, and other hazards. Lactic acid also significantly affects the taste of the meat for the worse.
Halal meat tastes better, is more tender, healthier and stays fresh longer because the absence of blood makes it resistant to bacteria. From an economic point of view, Halal meat makes more sense too. Because less blood means that there is more meat pound per pound, which yields more finished product to the consumer.
Also, the halal method of preparing animals is not only the most hygienic but also the most humane for the animal.