The Absolute and SlimFit proteins are whey-based which means they are derived from whole milk. Total Vegan is plant-based being derived from Pea, Rice, Hemp, Chia Seed and Cranberry. Obviously plant-based is more suitable for a vegan diet or if you are have a sensitivty to casein.
SlimFit is better suited for Weight Loss while Absolute is better suited for muscle-building and physical performance. Absolute is the best cost value per serving since you get about 39 servings per canister vs 21 for SlimFit and 14 for Total Vegan. You can of course slightly decrease the amount of powder per scoop to get more servings per container albeit with a corresponding reduction in nutrient values.