whey is fact acting, usually for after workouts
cassein is slow digesting mostly used at night so you dont fast while seelping
soy is for those with milk allegins though im not sure on its...
Optimum sells whey and oats together. I use 2 scoops of it every morning with 2 tbsp of natural no sugar added peanut butter mixed in 8 oz skim milk and 4 oz water.