In my opinion, vegetarianism is definitely not better than veganism on a global level. In fact , I would say it's somehow worse than eating meat. The dairy cows will be slaughtered or left to die once they can't produce any more milk, which would be at 5 years old. They die and they don't even feed anyone. Remember, veganism is an ideology, vegetarianism is a restrictive diet. they wouldn't care about the byproduct of the dairy industry which is the animal. Not to mention, it's very exploitative. For both people and animals. Animals will go through sexual abuse, being trapped, being abused, killed or what not. On ethical grounds, vegetarianism is just as bad, if not worse than carnism. It's a farce to make people believe they're helping the animals when they're only contributing to the industry that exploits them.

Concerning the human population, the amount of grain, water and land that would go to livestock will ultimately cost people food and housing. it will further exploit indigenous land and add to deforestation. Most AnAg driven deforestation happens because of dairy. Not to mention, the water wastage, energy wastage and what not. It's just exploiting the resources more and more.

Is veganism the perfect solution? Absolutely not. As long as capitalism exists, the world's problems will too. but it's much much better than both carnism and vegetarianism.