Being in the meat industry, I would say that raw is the standard(probably 85% in Chicago). Precooked is used for mostly chains,non-pizza restaurants, schools, etc. There's nothing really wrong with the other stuff, it just has added soy flour and is precooked, which takes away from adding more flavor to the sauce.
Also, if using raw, you can use it under the cheese. Just remember how much heat is in there. The stone is super hot and the heat of the oven combine to cook from the top and bottom very efficiently. I use either thick but small bits of sausage, or big flat (the thickness of 1-2 quarters) pieces about 2inches wide. I preheat the stone for an hour at 500 and then on broil for 15 minutes before cooking. This has always produced thoroughly cooked sausage.