Regardless of how much land and water it takes for meat versus vegetables, we need both meat and vegetables to be healthy. There is an abundance of land that is ill suited for raising vegetables which could be used for grazing and the production of healthy meat - and when you raise meat healthily you actually need consume much less than is the case with unhealthy factory farm animals, perhaps as little as half as much.
There is room for both and a need for both - it is simply a matter of proper balancing and healthy sustainable practices.