Pulao and Biryani are as different as chalk and cheese( Maybe not chalk but you get the idea). Biryani is made by draining the water out of the rice method. You could also parboil the rice and layer it up with your meat or the vegetables. Then the layers are cooked on low flame maybe in a sealed container . The amount of spices used also differs generally biryani use a little more. The marinade add to the gravy in a biryani than a pulao. That is why your biryani is more aromatic and richer. Since the Biryani is slow cooked it takes time to cook. A pulao, on the other hand you add your vegetables, meats and rice cook it all in  stock or water.This is called absorption method. Since pulao can be cooked on medium flame you have a faster cooked delicious rice dish.