Have you ever wondered if there is a difference between white and black pepper? The short answer is YES!
Both types of peppercorns come from the very same plant, piper nigrum. The difference is the way they are handled and ultimately their taste.
Black peppercorns are unripe berries that are picked and dried until the outer layer of skin turns black. White peppercorns are not picked until they are fully ripened. Then they are soaked in water and the outer skins removed, therefore the end product is cleaner.
But does the process make them TASTE different? Yes it does. The black peppercorns are more spicy, while the white peppercorns are "more floral and earthy" according to Cook's Illustrated. The white is also more expensive because of the extra steps to process it.
So what to choose when cooking?
White pepper - to maintain the light color of a dish.
Normally light colored soups, Vicyssoise for example would be a good dish to use white pepper.
Black pepper - if a larger amount is called for in a recipe.
Usually most recipes call for black pepper because it is much more common and they add it is for the spiciness factor. You will not get the same results with white pepper. Using white will change the flavor - while black increases spice!